Exhibit 1.1
                                                        [Draft as of 1/15/97]

                               2,000,000 Shares
 
                           PHOTOELECTRON CORPORATION

                                 Common Stock



                            UNDERWRITING AGREEMENT
                            ----------------------

                                                            January __, 1997


Needham & Company, Inc.
Dain Bosworth Incorporated
 As Representatives of the several Underwriters
 c/o Needham & Company, Inc.
 445 Park Avenue
 New York, New York 10022

Ladies and Gentlemen:

     Photoelectron Corporation, a Massachusetts corporation (the "Company"),
proposes to issue and sell an aggregate of 2,000,000 shares (the "Firm Shares")
of the Company's Common Stock, $.01 par value per share (the "Common Stock"), to
you and to the several other Underwriters named in Schedule I hereto
(collectively, the "Underwriters"), for whom you are acting as representatives
(the "Representatives").  The Company has also agreed to grant to you and the
other Underwriters an option (the "Option") to purchase up to an additional
300,000 shares of Common Stock, on the terms and for the purposes set forth in
Section 1(b) (the "Option Shares").  The Firm Shares and the Option Shares are
referred to collectively herein as the "Shares."

     The Company confirms as follows its agreement with the Representatives and
the several other Underwriters.

     1.    Agreement to Sell and Purchase.

     (a)   On the basis of the representations, warranties and agreements of the
Company herein contained and subject to all the terms and conditions of this
Agreement, (i) the Company agrees to issue and sell the Firm Shares to the
several Underwriters and (ii) each of the Underwriters, severally and not
jointly, agrees to purchase from the Company the respective number of Firm
Shares set forth opposite that Underwriter's name in Schedule I hereto, at the
purchase price of [$12] for each Firm Share.

     (b)   Subject to all the terms and conditions of this Agreement, the
Company grants the Option to the several Underwriters to purchase, severally and
not jointly, up to an aggregate of 300,000 Option Shares at the same price per
share as the Underwriters shall pay for the Firm Shares. The Option may be
exercised only to cover over-allotments in the sale of the Firm Shares by the
Underwriters and may be exercised in whole or in part at any time (but not more
than once) on or before the 30th day after the date of this Agreement upon
written or telegraphic notice (the "Option Shares Notice") by the
Representatives to the Company no later than 12:00 noon, New York City time, at
least two and no

- --------------------------
*     Plus an option purchase up to additional 300,000 shares to cover 
      over-allotments.

                                       1

 
more than five business days before the date specified for closing in the Option
Shares Notice (the "Option Closing Date"), setting forth the aggregate number of
Option Shares to be purchased and the time and date for such purchase. On the
Option Closing Date, the Company will issue and sell to the Underwriters the
number of Option Shares set forth in the Option Shares Notice, and each
Underwriter will purchase such percentage of the Option Shares as is equal to
the percentage of Firm Shares that such Underwriter is purchasing, as adjusted
by the Representatives in such manner as they deem advisable to avoid fractional
shares.

     2.   Delivery and Payment. Delivery of the Firm Shares shall be made to the
Representatives for the accounts of the Underwriters against payment of the
purchase price by certified or official bank checks or by wire transfer payable
in same-day funds to the order of the Company at the office of Needham &
Company, Inc., 445 Park Avenue, New York, New York 10022, at 10:00 a.m., New
York City time, on the third (or, if the purchase price set forth in Section
1(b) hereof is determined after 4:30 p.m., Washington D.C. time, the fourth)
business day following the commencement of the offering contemplated by this
Agreement, or at such time on such other date, not later than seven business
days after the date of this Agreement, as may be agreed upon by the Company and
the Representatives (such date is hereinafter referred to as the "Closing
Date").

     To the extent the Option is exercised, delivery of the Option Shares
against payment by the Underwriters (in the manner specified above) will take
place at the offices specified above for the Closing Date at the time and date
(which may be the Closing Date) specified in the Option Shares Notice.

     Certificates evidencing the Shares shall be in definitive form and shall be
registered in such names and in such denominations as the Representatives shall
request at least two business days prior to the Closing Date or the Option
Closing Date, as the case may be, by written notice to the Company.  For the
purpose of expediting the checking and packaging of certificates for the Shares,
the Company agrees to make such certificates available for inspection at least
24 hours prior to the Closing Date or the Option Closing Date, as the case may
be.

     The cost of original issue tax stamps, if any, in connection with the
issuance and delivery of the Firm Shares and Option Shares by the Company to the
respective Underwriters shall be borne by the Company.  The Company will pay and
save each Underwriter and any subsequent holder of the Shares harmless from any
and all liabilities with respect to or resulting from any failure or delay in
paying Federal and state stamp and other transfer taxes, if any, which may be
payable or determined to be payable in connection with the original issuance or
sale to such Underwriter of the Shares.

     3.   Representations and Warranties of the Company. The Company represents,
warrants and covenants to each Underwriter that:

     (a)  A registration statement (Registration No. 333-14541) on Form S-1
relating to the Shares, including a preliminary prospectus and any amendments to
such registration statement, has been prepared by the Company under the
provisions of the Securities Act of 1933, as amended (the "Act"), and the rules
and regulations (collectively referred to as the "Rules and Regulations") of the
Securities and Exchange Commission (the "Commission") thereunder, and has been
filed with the Commission. The term "preliminary prospectus" as used herein
means a preliminary prospectus as contemplated by Rule 430 or Rule 430A of the
Rules and Regulations included at any time as part of the registration
statement. Copies of such registration statement and amendments and of each
related preliminary prospectus have been delivered to the Representatives. If
such registration statement has not become effective, a further amendment to
such registration statement, including a form of final prospectus, necessary to
permit such registration statement to become effective will be filed promptly by
the Company with the Commission. If such registration statement has become
effective, a final prospectus containing information permitted to be omitted at
the time of effectiveness by Rule 430A of the Rules and Regulations will be
filed promptly by the Company with the Commission in accordance with Rule 424(b)
of the Rules and Regulations. The term "Registration Statement" means the
registration statement as amended at the time it becomes or became effective
(the "Effective Date"), including financial statements and all exhibits and any
information deemed to be included by Rule 430A and includes any registration
statement relating to the offering contemplated by this Agreement and filed
pursuant to Rule 462(b) of the Rules and Regulations. The term "Prospectus"
means the prospectus as first filed with the Commission pursuant to Rule 424(b)
of the Rules and 

                                       2

 
Regulations or, if no such filing is required, the form of final prospectus
included in the Registration Statement at the Effective Date.
 
     (b)  No order preventing or suspending the use of the preliminary
prospectus of the Company has been issued by the Commission. On the Effective
Date, the date the Prospectus is first filed with the Commission pursuant to
Rule 424(b) (if required), at all times subsequent thereto to and including the
Closing Date and, if later, the Option Closing Date and when any post-effective
amendment to the Registration Statement becomes effective or any amendment or
supplement to the Prospectus is filed with the Commission, the Registration
Statement and the Prospectus (as amended or as supplemented if the Company shall
have filed with the Commission any amendment or supplement thereto), including
the financial statements included in the Prospectus, did and will comply with
all applicable provisions of the Act and the Rules and Regulations and will
contain all statements required to be stated therein in accordance with the Act
and the Rules and Regulations. On the Effective Date and when any post-effective
amendment to the Registration Statement becomes effective, no part of the
Registration Statement, the Prospectus or any such amendment or supplement did
or will contain an untrue statement of a material fact or omit to state a
material fact required to be stated therein or necessary in order to make the
statements therein not misleading. At the Effective Date, the date the
Prospectus or any amendment or supplement to the Prospectus is filed with the
Commission and at the Closing Date and, if later, the Option Closing Date, the
Prospectus did not and will not contain any untrue statement of a material fact
or omit to state a material fact necessary to make the statements therein, in
the light of the circumstances under which they were made, not misleading. The
foregoing representations and warranties in this Section 3(b) do not apply to
any statements or omissions made in reliance on and in conformity with
information relating to any Underwriter furnished in writing to the Company by
the Representatives specifically for inclusion in the Registration Statement or
Prospectus or any amendment or supplement thereto. The Company acknowledges that
the statements set forth under the heading "Underwriting" in the Prospectus and
"Underwriting Discounts and Commissions" on the cover page of the Prospectus or
any amendment or supplement thereto constitute the only information relating to
any Underwriter furnished in writing to the Company by the Representatives
specifically for inclusion in the Registration Statement.

     (c)  The Company does not own, and at the Closing Date and, if later, the
Option Closing Date, will not own, directly or indirectly, any shares of stock
or any other equity or long-term debt securities of any corporation or have any
equity interest in any corporation, firm, partnership, joint venture,
association or other entity, other than the subsidiaries listed in Exhibit 21 to
the Registration Statement (the "Subsidiaries"). The Company and each of its
Subsidiaries is, and at the Closing Date and, if later, the Option Closing Date,
will be, a corporation duly organized, validly existing and in good standing
under the laws of its jurisdiction of incorporation. The Company and each of its
Subsidiaries has, and at the Closing Date and, if later, the Option Closing
Date, will have, full power and authority to conduct all the activities
conducted by it, to own or lease all the assets owned or leased by it and to
conduct its business as described in the Registration Statement and the
Prospectus. The Company and each of its Subsidiaries is, and at the Closing Date
and, if later, the Option Closing Date, will be, duly licensed or qualified to
do business and in good standing as a foreign corporation in all jurisdictions
in which the nature of the activities conducted by it or the character of the
assets owned or leased by it makes such license or qualification necessary,
except to the extent that the failure to be so qualified or be in good standing
would not materially and adversely affect the Company or its business,
properties, business prospects, condition (financial or other) or results of
operations. All of the outstanding shares of capital stock of each Subsidiary
have been duly authorized and validly issued and are fully paid and
nonassessable, and owned by the Company free and clear of all claims, liens,
charges and encumbrances; there are no securities outstanding that are
convertible into or exercisable or exchangeable for capital stock of any
Subsidiary. The Company is not, and at the Closing Date and, if later, the
Option Closing Date, will not be, engaged in any discussions or a party to any
agreement or understanding, written or oral, regarding the acquisition of an
interest in any corporation, firm, partnership, joint venture, association or
other entity where such discussions, agreements or understandings would require
amendment to the Registration Statement pursuant to applicable securities laws.
Complete and correct copies of the Articles of Organization and of the By-laws
of the Company and each of its Subsidiaries and all amendments thereto have been
delivered to the Representatives, and no changes therein will be made subsequent
to the date hereof and prior to the Closing Date or, if later, the Option
Closing Date.

                                       3

 
     (d)  All of the outstanding shares of capital stock of the Company have
been duly authorized, validly issued and (except as otherwise described in Item
15 of the Registration Statement) are fully paid and nonassessable and were
issued in compliance with all applicable state and federal securities laws; the
Shares have been duly authorized and when issued and paid for as contemplated
herein will be validly issued, fully paid and nonassessable; no preemptive or
similar rights exist with respect to any of the Shares or the issue and sale
thereof. The description of the capital stock of the Company in the Registration
Statement and the Prospectus is, and at the Closing Date and, if later, the
Option Closing Date, will be, complete and accurate in all material respects.
Except as set forth in the Prospectus, the Company does not have outstanding,
and at the Closing Date and, if later, the Option Closing Date, will not have
outstanding, any options to purchase, or any rights or warrants to subscribe
for, or any securities or obligations convertible into, or any contracts or
commitments to issue or sell, any shares of capital stock, or any such warrants,
convertible securities or obligations. No further approval or authority of
stockholders or the Board of Directors of the Company will be required for the
issuance and sale of the Shares as contemplated herein.
 
     (e)  The financial statements and schedules included in the Registration
Statement or the Prospectus present fairly in all material respects the
financial condition of the Company and its consolidated Subsidiaries as of the
respective dates thereof and the results of operations and cash flows of the
Company and its consolidated Subsidiaries for the respective periods covered
thereby, all in conformity with generally accepted accounting principles applied
on a consistent basis throughout the entire period involved, except as otherwise
disclosed in the Prospectus.  No other financial statements or schedules of the
Company are required by the Act or the Rules and Regulations to be included in
the Registration Statement or the Prospectus.  Arthur Andersen LLP (the
"Accountants"), who have reported on such financial statements and schedules,
are independent accountants with respect to the Company as required by the Act
and the Rules and Regulations.  The summary consolidated financial and
statistical data included in the Registration Statement present fairly the
information shown therein and have been compiled on a basis consistent with the
financial statements presented therein.

     (f)  Subsequent to the respective dates as of which information is given in
the Registration Statement and the Prospectus and prior to the Closing Date and,
if later, the Option Closing Date, except as set forth in or contemplated by the
Registration Statement and the Prospectus, (i) there has not been and will not
have been any change in the capitalization of the Company (other than in
connection with (a) the exercise of options to purchase the Company's Common
Stock granted pursuant to the Company's stock option plan from the shares
reserved therefor as described in the Registration Statement) or (b) the
exercise of the warrants or the convertible debt described in the Registration
Statement), or any material adverse change in the business, properties, business
prospects, condition (financial or otherwise) or results of operations of the
Company or any of its Subsidiaries, taken as a whole, arising for any reason
whatsoever; (ii) the Company has not incurred nor will it incur, except in the
ordinary course of business as described in the Prospectus, any liabilities or
obligations, direct or contingent that are material to the Company and its
Subsidiaries taken as a whole, nor has the Company or any of its Subsidiaries
entered into nor will it enter into, except in the ordinary course of business
as described in the Prospectus, any transactions other than pursuant to this
Agreement and the transactions referred to herein that are material to the
Company and its Subsidiaries taken as a whole; and (iii) the Company has not and
will not have paid or declared any dividends or other distributions of any kind
on any class of its capital stock.
 
     (g)  The Company is not, will not become as a result of the transactions
contemplated hereby, and does not intend to conduct its business in a manner
that would cause it to become, an "investment company" or an "affiliated person"
of, or "promoter" or "principal underwriter" for, an "investment company," as
such terms are defined in the Investment Company Act of 1940, as amended.

     (h)  Except as set forth in the Registration Statement and the Prospectus,
there are no actions, suits or proceedings pending or, to the knowledge of the
Company, threatened against the Company, any of its Subsidiaries or any of its
or their officers in their capacity as such, before or by any Federal or state
court, commission, regulatory body, administrative agency or other governmental
body, domestic or foreign, wherein an unfavorable ruling, decision or finding
would reasonably be expected to materially and adversely affect the Company, any
of its Subsidiaries or the business, properties, business prospects, condition
(financial or otherwise) or results of operations of the Company or any of its
Subsidiaries taken as a whole.

                                       4

 
     (i)  The Company and each Subsidiary has, and at the Closing Date and, if
later, the Option Closing Date, will have, performed all the obligations
required to be performed by it, and is not, and at the Closing Date, and, if
later, the Option Closing Date, will not be, in default, under any contract or
other instrument to which it is a party or by which its property is bound or
affected, which default would reasonably be expected to materially and adversely
affect the Company or the business, properties, business prospects, condition
(financial or other) or results of operations of the Company or any of its
Subsidiaries taken as a whole. To the best knowledge of the Company, no other
party under any contract or other instrument to which it or any of its
Subsidiaries is a party is in default in any respect thereunder, which default
would reasonably be expected to materially and adversely affect the Company, any
of its Subsidiaries or the business, properties, business prospects, condition
(financial or other) or results of operations of the Company or any of its
Subsidiaries taken as a whole. The Company is not, and at the Closing Date and,
if later, the Option Closing Date, will not be, in violation of any provision of
its Articles of Incorporation or By-laws.

     (j)  No consent, approval, authorization or order of, or any filing or
declaration with, any court or governmental agency or body is required for the
consummation by the Company of the transactions on its part contemplated herein,
except such as have been obtained under the Act or the Rules and Regulations and
such as may be required under state securities or Blue Sky laws or the by-laws
and rules of the National Association of Securities Dealers, Inc. (the "NASD")
in connection with the purchase and distribution by the Underwriters of the
Shares.

     (k)  The Company has full corporate power and authority to enter into this
Agreement. This Agreement has been duly authorized, executed and delivered by
the Company and constitutes a valid and binding agreement of the Company,
enforceable against the Company in accordance with the terms hereof. The
performance of this Agreement and the consummation of the transactions
contemplated hereby will not result in the creation or imposition of any lien,
charge or encumbrance upon any of the assets of the Company pursuant to the
terms or provisions of, or result in any material respect in a breach or
violation of any of the terms or provisions of, or constitute a default in any
material respect under, or give any party a right to terminate any of its
obligations under, or result in the acceleration of any obligation under, the
certificate or Articles of Organization or by-laws of the Company or any of its
Subsidiaries, any indenture, mortgage, deed of trust, voting trust agreement,
loan agreement, bond, debenture, note agreement or other evidence of
indebtedness, lease, contract or other agreement or instrument to which the
Company or any of its Subsidiaries is a party or by which the Company, any of
its Subsidiaries or any of its or their properties is bound or affected, or
violate or conflict in any material respect with any judgment, ruling, decree,
order, statute, rule or regulation of any court or other governmental agency or
body applicable to the business or properties of the Company or any of its
Subsidiaries taken as a whole.

     (l)  The Company has good and marketable title to all properties and assets
described in the Prospectus as owned by it, free and clear of all liens,
charges, encumbrances or restrictions, except such as are described in the
Prospectus or are not material to the business of the Company or its
Subsidiaries taken as a whole. The Company has valid, subsisting and enforceable
leases for the properties described in the Prospectus as leased by it. The
Company owns or leases all such properties as are necessary to its operations as
now conducted or as proposed to be conducted through and including calendar year
1999, except where the failure to so own or lease would not materially and
adversely affect the business, properties, business prospects, condition
(financial or otherwise) or results of operations of the Company.
 
     (m)  There is no document or contract of a character required by the Act to
be described in the Registration Statement or the Prospectus or to be filed as
an exhibit to the Registration Statement which is not described or filed as
required. All such contracts to which the Company is a party which were filed as
Exhibits to the Registration Statement have been duly authorized, executed and
delivered by the Company, constitute valid and binding agreements of the Company
and are enforceable against and by the Company in accordance with the terms
thereof.

     (n)  No statement, representation, warranty or covenant made by the Company
in this Agreement or made in any certificate or document required by Section 4
of this Agreement to be delivered to the Representatives was or will be, when
made, inaccurate, untrue or incorrect.

                                       5

 
     (o)  Neither the Company nor to its knowledge any of its directors,
officers or controlling persons has taken, directly or indirectly, any action
designed, or which might reasonably be expected, to cause or result, under the
Act or otherwise, in, or which has constituted, stabilization or manipulation of
the price of any security of the Company to facilitate the sale or resale of the
Shares.

     (p)  No holder of securities of the Company has rights to the registration
of any securities of the Company because of the filing of the Registration
Statement, which rights have not been waived by the holder thereof as of the
date hereof.

     (q)  The Company has filed a registration statement pursuant to Section
12(g) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"),
to register the Common Stock, has filed an application to list the Shares on the
Nasdaq National Stock Market ("NNM"), and has received notification that the
listing has been approved, subject to notice of issuance of the Shares.

     (r)  Except as disclosed in or specifically contemplated by the Prospectus
(i) the Company owns or possesses all trademarks, trade names, patent rights,
mask works, copyrights, licenses, approvals and governmental authorizations as
described in the Prospectus and necessary to conduct its business as now
conducted, (ii) the Company has no knowledge of any infringement by it or any of
its Subsidiaries of trademarks, trade name rights, patent rights, mask work
rights, copyrights, licenses, trade secrets or other similar rights of others,
where such infringement would reasonably be expected to have a material and
adverse effect on the Company or the business, properties, business prospects,
condition (financial or otherwise) or results of operations of the Company, and
(iii) no claim has been made against the Company, or to the best of the
Company's knowledge, any employee of the Company, regarding trademark, trade
name, patent, mask work, copyright, license, trade secret or other infringement
which would reasonably be expected to have a material and adverse effect on the
Company or the business, properties, business prospects, condition (financial or
otherwise) or results of operations of the Company.

     (s)  The Company and each of its Subsidiaries has filed all federal, state,
local and foreign income tax returns which have been required to be filed and
has paid all taxes shown as due on such returns and has paid all assessments
received by it to the extent that such taxes or assessments have become due,
except where the failure to file such return, pay such taxes, or assessment
would not be reasonably expected to have a material adverse effect on the
Company or its Subsidiaries taken as a whole. Neither the Company nor any of its
Subsidiaries has any tax deficiency which has been or, to the best knowledge of
the Company, might be asserted or threatened against it which would reasonably
be expected to have a material and adverse effect on the business, properties,
business prospects, condition (financial or otherwise) or results of operations
of the Company or its Subsidiaries taken as a whole.
 
     (t)  The pro forma financial information set forth on pages 16 and 18 in
the Registration Statement accurately reflects, subject to the limitations set
forth in the Registration Statement as to such pro forma financial information,
that such statements present fairly the information purported to be shown
therein at the respective dates or for the respective periods therein specified.
 
     (u)  Except as disclosed in the Prospectus, the Company owns or possesses
all authorizations, approvals, orders, licenses, registrations, other
certificates and permits of and from all governmental regulatory officials and
bodies, necessary under applicable law to conduct its business as contemplated
in the Prospectus, except where the failure to own or possess all such
authorizations, approvals, orders, licenses, registrations, other certificates
and permits would not materially and adversely affect the Company or the
business, properties, business prospects, condition (financial or otherwise) or
results of operations of the Company. Except as disclosed in the Prospectus,
there is no proceeding pending or threatened (or any basis therefor known to the
Company) which would reasonably be expected to cause any such authorization,
approval, order, license, registration, certificate or permit to be revoked,
withdrawn, canceled, suspended or not renewed; and the Company is conducting its
business in compliance with all laws, rules and regulations applicable thereto
(including, without limitation, all applicable federal, state and local
environmental laws and regulations) except where such noncompliance would not
materially and adversely affect the Company or the business, properties,
business prospects, condition (financial or otherwise) or results of operations
of the Company or any of its Subsidiaries taken as a whole.

                                       6

 
     (v)  The Company maintains insurance of the types and in the amounts
generally deemed adequate for its business, including, but not limited to,
insurance covering real and personal property owned or leased by the Company
against theft, damage, destruction, acts of vandalism and all other risks
customarily insured against, all of which insurance is in full force and effect.
 
     (w)  Neither the Company nor any of its Subsidiaries has nor, to the
Company's knowledge, any of its or their respective employees or agents at any
time during the last five years (i) made any unlawful contribution to any
candidate for foreign office, or failed to disclose fully any contribution in
violation of law, or (ii) made any payment to any federal or state governmental
officer or official, or other person charged with similar public or quasi-public
duties, other than payments required or permitted by the laws of the United
States or any jurisdiction thereof.

     4.   Agreements of the Company.  The Company covenants and agrees with the
several Underwriters as follows:

     (a)  The Company will not, either prior to the Effective Date or thereafter
during such period as the Prospectus is required by law to be delivered in
connection with sales of the Shares by an Underwriter or dealer, file any
amendment or supplement to the Registration Statement or the Prospectus, unless
a copy thereof shall first have been submitted to the Representatives within a
reasonable period of time prior to the proposed filing date
thereof and the Representatives shall not have objected thereto in good
faith prior to such proposed filing date.

     (b)  The Company will use its best efforts to cause the Registration
Statement to become effective, and will notify the Representatives promptly, and
will confirm such advice in writing, (i) when the Registration Statement has
become effective and when any post-effective amendment thereto becomes
effective, (ii) of any request by the Commission for amendments or supplements
to the Registration Statement or the Prospectus or for additional information,
(iii) of the issuance by the Commission of any stop order suspending the
effectiveness of the Registration Statement or the initiation of any proceedings
for that purpose or the threat thereof, and (iv) of the happening of any event
during the period mentioned in the second sentence of Section 4(e) that in the
judgment of the Company makes any statement made in the Registration Statement
or the Prospectus untrue or that requires the making of any changes in the
Registration Statement or the Prospectus in order to make the statements
therein, in the light of the circumstances in which they are made, not
misleading. If at any time the Commission shall issue any order suspending the
effectiveness of the Registration Statement, the Company will make every
reasonable effort to obtain the withdrawal of such order at the earliest
possible moment. If the Company has omitted any information from the
Registration Statement required pursuant to Rule 430A of the Rules and
Regulations, the Company will comply with the provisions of and make all
requisite filings with the Commission pursuant to said Rule 430A and notify the
Representatives promptly of all such filings.
 
     (c)  The Company will furnish to each Representative, without charge, one
signed copy of each of the Registration Statement and of any post-effective
amendment thereto, including financial statements and schedules, and all
exhibits thereto and will furnish to the Representatives, without charge, for
transmittal to each of the other Underwriters, a copy of the Registration
Statement and any post-effective amendment thereto, including financial
statements and schedules but without exhibits.
 
     (d)  The Company will comply with all the provisions of any undertakings
contained in the Registration Statement.

     (e)  On the Effective Date, and thereafter from time to time, the Company
will deliver to each of the Underwriters, without charge, as many copies of the
Prospectus or any amendment or supplement thereto as the Representatives may
reasonably request. The Company consents to the use of the Prospectus or any
amendment or supplement thereto by the several Underwriters and by all dealers
to whom the Shares may be sold, both in connection with the offering or sale of
the Shares and for any period of time thereafter during which the Prospectus is
required by law to be delivered in connection therewith. If during such period
of time any event shall occur which in the judgment of the Company or counsel to
the Underwriters should be set forth in the Prospectus in order to make any
statement 

                                       7

 
therein, in the light of the circumstances under which it was made, not
misleading, or if it is necessary to supplement or amend the Prospectus to
comply with law, the Company will forthwith prepare and duly file with the
Commission an appropriate supplement or amendment thereto, and will deliver to
each of the Underwriters, without charge, such number of copies of such
supplement or amendment to the Prospectus as the Representatives may reasonably
request.

     (f)  Prior to any public offering of the Shares, the Company will cooperate
with the Representatives and counsel to the Underwriters in connection with the
registration, qualification, or exemption of the Shares for offer and sale under
the securities or Blue Sky laws of such jurisdictions as the Representatives may
request; provided, that in no event shall the Company be obligated to qualify to
do business in any jurisdiction where it is not now so qualified or to take any
action which would subject it to general service of process in any jurisdiction
where it is not now so subject.
 
     (g)  The Company will, so long as required under the Rules and Regulations,
furnish to its stockholders as soon as practicable after the end of each fiscal
year an annual report (including a balance sheet and statements of income,
stockholders' equity and cash flow of the Company and its consolidated
Subsidiaries, if any, certified by independent public accountants) and, as soon
as practicable after the end of each of the first three quarters of each fiscal
year (beginning with the fiscal quarter ending after the effective date of the
Registration Statement), consolidated summary financial information of the
Company and its Subsidiaries, if any, for such quarter in reasonable detail.
 
     (h)  During the period of five years commencing on the Effective Date, the
Company will furnish to the Representatives and each other Underwriter who may
so request copies of such financial statements and other periodic and special
reports as the Company may from time to time distribute generally to the holders
of any class of its capital stock, and will furnish to the Representatives and
each other Underwriter who may so request a copy of each annual or other report
it shall be required to file with the Commission.

     (i)  The Company will make generally available to holders of its securities
as soon as may be practicable but in no event later than the last day of the
fifteenth full calendar month following the calendar quarter in which the
Effective Date falls, an earnings statement (which need not be audited but shall
be in reasonable detail) for a period of 12 months ended commencing after the
Effective Date, and satisfying the provisions of Section 11(a) of the Act
(including Rule 158 of the Rules and Regulations).
 
     (j)  Whether or not the transactions contemplated by this Agreement are
consummated or this Agreement is terminated, the Company will pay or reimburse
if paid by the Representatives all costs and expenses arising from the
performance of the obligations of the Company under this Agreement and in
connection with the transactions contemplated hereby, including but not limited
to costs and expenses of or relating to (i) the preparation, printing and filing
of the Registration Statement and exhibits to it, each preliminary prospectus,
Prospectus and any amendment or supplement to the Registration Statement or
Prospectus, (ii) the preparation and delivery of certificates representing the
Shares, (iii) the printing of this Agreement, the Agreement Among Underwriters,
any Selected Dealer Agreements, any Underwriters' Questionnaires, any
Underwriters' Powers of Attorney, and any invitation letters to prospective
Underwriters, (iv) furnishing (including costs of shipping and mailing) such
copies of the Registration Statement, the Prospectus and any preliminary
prospectus, and all amendments and supplements thereto, as may be requested for
use in connection with the offering and sale of the Shares by the Underwriters
or by dealers to whom Shares may be sold, (v) the listing of the Shares on the
NNM, (vi) any filings required to be made by the Underwriters with the NASD, and
the fees, disbursements and other charges of counsel for the Underwriters in
connection therewith, (vii) the registration or qualification of the Shares for
offer and sale under the securities or Blue Sky laws of such jurisdictions
designated pursuant to Section 4(f), including the fees, disbursements and other
charges of counsel to the Underwriters in connection therewith, and the
preparation and printing of preliminary, supplemental and final Blue Sky
memoranda, (viii) fees, disbursements and other charges of counsel to the
Company (but not those of counsel for the Underwriters, except as otherwise
provided herein) and (ix) the transfer agent for the Shares.

     (k)  The Company will not at any time, directly or indirectly, take any
action designed or which might reasonably be expected to cause or result in, or
which will constitute, stabilization of the price of the shares of Common Stock
to facilitate the sale or resale of any of the Shares.

                                       8

 
     (l)  The Company will apply the net proceeds from the offering and sale of
the Shares to be sold by the Company in the manner set forth in the Prospectus
under "Use of Proceeds" and shall file such reports with the Commission with
respect to the sale of the Shares and the application of the proceeds therefrom
as may be required in accordance with Rule 463 under the Act.
 
     (m)  During the period beginning from the date hereof and continuing to and
including the date 180 days after the date of the Prospectus, without the prior
written consent of Needham & Company, Inc., the Company will not offer, sell,
contract to sell, grant options to purchase or otherwise dispose of any of the
Company's equity securities of the Company or any other securities convertible
into or exchangeable with its Common Stock or other equity security (other than
pursuant to employee stock option plans or the conversion of convertible
securities or the exercise of warrants or convertible debt outstanding on the
date of this Agreement).

     (n)  During the period of 180 days after the date of the Prospectus, the
Company will not, without the prior written consent of Needham & Company, Inc.,
grant options to purchase shares of Common Stock at a price less than the
initial public offering price. During the period of 180 days after the date of
the Prospectus, the Company will not file with the Commission or cause to become
effective any registration statement relating to any securities of the Company
without the prior written consent of Needham & Company, Inc., except as
contemplated by Paragraph 4(p).

     (o)  The Company will cause each of its officers, directors and certain
stockholders designated by the Representatives to enter into lock-up agreements
with the Representatives to the effect that they will not, without the prior
written consent of Needham & Company, Inc., sell, contract to sell or otherwise
dispose of any shares of Common Stock or rights to acquire such shares
according to the terms of an agreement to be substantially similar to the
terms set forth in Schedule II hereto.

     (p)  The Company will not file with the Commission any registration
statement on Form S-8 relating to shares of its Common Stock prior to 90 days
after the effective date of the Registration Statement.
 
     5.   Conditions of the Obligations of the Underwriters. The obligations of
each Underwriter hereunder are subject to the following conditions:
 
     (a)  Notification that the Registration Statement has become effective
shall be received by the Representatives not later than 5:00 p.m., New York City
time, on the date of this Agreement or at such later date and time as shall be
consented to in writing by the Representatives and all filings required by Rule
424 and Rule 430A of the Rules and Regulations shall have been made.

     (b)  (i) No stop order suspending the effectiveness of the Registration
Statement shall have been issued and no proceedings for that purpose shall be
pending or threatened by the Commission, (ii) no order suspending the
effectiveness of the Registration Statement or the qualification, registration,
or exemption of the Shares under the securities or Blue Sky laws of any
jurisdiction shall be in effect and no proceeding for such purpose shall be
pending before or threatened or contemplated by the Commission or the
authorities of any such jurisdiction, (iii) any request for additional
information on the part of the staff of the Commission or any such authorities
shall have been complied with to the satisfaction of the staff of the Commission
or such authorities and (iv) after the date hereof no amendment or supplement to
the Registration Statement or the Prospectus shall have been filed unless a copy
thereof was first submitted to the Representatives and the Representatives do
not object thereto within a reasonable period of time in good faith, and
the Representatives shall have received certificates, dated the Closing Date
and, if later, the Option Closing Date and signed by the Chief Executive Officer
and the Chief Financial Officer of the Company (who may, as to proceedings
threatened, rely upon the best of their information and belief), to the effect
of clauses (i), (ii) and (iii) of this paragraph.

     (c)  Since the respective dates as of which information is given in the
Registration Statement and the Prospectus, (i) there shall not have been a
material adverse change in the general affairs, business, business prospects,
properties, management, condition (financial or otherwise) or results of
operations of the Company or any of its Subsidiaries taken as a whole, whether
or not arising from transactions in the ordinary course of business, in each
case 

                                       9

 
other than as described in or contemplated by the Registration Statement and the
Prospectus, and (ii) the Company shall not have sustained any material loss or
interference with its business or properties, taken as a whole, from fire,
explosion, flood or other casualty, whether or not covered by insurance, or from
any labor dispute or any court or legislative or other governmental action,
order or decree, which is not described in the Registration Statement and the
Prospectus, which in the judgment of the Representatives any such development
makes it impracticable or inadvisable to consummate the sale and delivery of the
Shares by the Underwriters at the initial public offering price.
 
     (d)  Since the respective dates as of which information is given in the
Registration Statement and the Prospectus, there shall have been no litigation
or other proceeding instituted against the Company, any of its Subsidiaries, or
any of its or their officers or directors in their capacities as such, before or
by any Federal, state or local court, commission, regulatory body,
administrative agency or other governmental body, domestic or foreign, in which
litigation or proceeding an unfavorable ruling, decision or finding would, in
the judgment of the Representatives, materially and adversely affect the
business, properties, business prospects, condition (financial or otherwise) or
results of operations of the Company or any of its Subsidiaries taken as a
whole.

     (e)  Each of the representations and warranties of the Company contained
herein shall be true and correct in all material respects at the Closing Date
and, with respect to the Option Shares, at the Option Closing Date, and all
covenants and agreements contained herein to be performed on the part of the
Company and all conditions contained herein to be fulfilled or complied with by
the Company at or prior to the Closing Date and, with respect to the Option
Shares, at or prior to the Option Closing Date, shall have been duly performed,
fulfilled or complied with.
     
     (f) The Representatives shall have received an opinion, dated the Closing
Date and, with respect to the Option Shares, the Option Closing Date,
satisfactory in form and substance to the Representatives and counsel for
the Underwriters from Goulston & Storrs, P.C., counsel to the Company, or
other counsel to the Company, with respect to the following matters,
subject to such limitations and qualifications as are agreed upon under the
circumstances, or as otherwise waived by the Underwriters:

          (i)  The Company and each of its Subsidiaries is a corporation duly
     organized, validly existing and in good standing under the laws of its
     jurisdiction of incorporation; has full corporate power and authority to
     conduct all the activities conducted by it, to own or lease all the assets
     owed or leased by it and to conduct its business as described in the
     Registration Statement and Prospectus; and is duly licensed or qualified to
     do business and is in good standing as a foreign corporation in all
     jurisdictions in which the nature of the activities conducted by it or the
     character of the assets owned or leased by it makes such license or
     qualification necessary and where the failure to be licensed or qualified
     would have a material and adverse effect on the business or financial
     condition of the Company.

          (ii)  All of the outstanding shares of capital stock of the Company
     issued prior to the effective date of the Registration Statement have been
     duly authorized, validly issued and are fully paid and nonassessable,
     except as disclosed in the Registration Statement and were not issued in
     violation of or subject to any preemptive or, to such counsel's knowledge,
     similar rights. All of the Firm Shares have been duly authorized, validly
     issued and are fully paid and non-assessable, and the Option Shares, if
     purchased by the Underwriters will, when so issued and sold, be duly
     authorized, validly issued and fully paid and non assessable.

          (iii) The specimen certificate evidencing the Common Stock filed as an
     exhibit to the Registration Statement is in due and proper form under the
     law of the Commonwealth of Massachusetts law, the Shares have been duly
     authorized and, when issued and paid for as contemplated by this Agreement,
     will be validly issued, fully paid and nonassessable; and no preemptive or
     similar rights exist with respect to any of the Shares or the issue and
     sale thereof.

          (iv)  To such counsel's knowledge, the Company does not own or
     control, directly or indirectly, any shares of stock or any other equity or
     long-term debt securities of any corporation or have any equity interest in
     any corporation, firm, partnership, joint venture, association or other
     entity. All of the outstanding shares of capital stock of each Subsidiary
     have been duly authorized and validly issued 

                                       10

 
    and are fully paid and nonassessable, and owned by the Company free and
    clear of all claims, liens, charges and encumbrances; to such counsel's
    knowledge, there are no securities outstanding that are convertible into or
    exercisable or exchangeable for capital stock of any Subsidiary.

        (v)     The authorized and outstanding capital stock of the Company is
    as set forth in the Registration Statement and the Prospectus in the column
    entitled "Actual" under the caption "Capitalization" (except for subsequent
    issuances or forfeitures, if any, pursuant to this Agreement or pursuant to
    reservations, agreements, employee benefit plans or the exercise of
    convertible securities or indebtedness, options or warrants referred to in
    the Prospectus). To such counsel's knowledge, except as disclosed in or
    specifically contemplated by the Prospectus, there are no outstanding
    options, warrants of other rights calling for the issuance of, and no
    commitments, plans or arrangements to issue, any shares of capital stock of
    the Company or any security convertible into or exchangeable or exercisable
    for capital stock of the Company. The description of the capital stock of
    the Company in the Registration Statement and the Prospectus conforms in all
    material respects to the terms thereof.

        (vi)    To such counsel's knowledge, there are no legal or governmental
    proceedings pending or threatened to which the Company or any of its
    Subsidiaries is a party or to which any of their respective properties is
    subject that are required to be described in the Registration Statement or
    the Prospectus but are not so described.

        (vii)   No consent, approval, authorization or order of, or any filing
    or declaration with, any court or governmental agency or body is required
    for the consummation by the Company of the transactions on its part
    contemplated under this Agreement except such as have been obtained or made
    under the Act or the Rules and Regulations and such as may be required under
    state securities or Blue Sky laws or the by-laws and rules of the NASD in
    connection with the purchase and distribution by the Underwriters of the
    Shares.

        (viii)  The Company has full corporate power and authority to enter into
    this Agreement. This Agreement has been duly authorized, executed and
    delivered by the Company.

        (ix)    The execution and delivery of this Agreement by the Company, the
    compliance by the Company with all of the terms hereof and the consummation
    of the transactions contemplated hereby does not contravene any provision of
    applicable law or the Articles of Organization or By-Laws of the Company or
    any of its Subsidiaries, and to the best of such counsel's knowledge will
    not result in the creation or imposition of any lien, charge or encumbrance
    upon any of the assets of the Company pursuant to the terms and provisions
    of, result in a breach or violation of any of the terms or provisions of, or
    constitute a default under, or give any party a right to terminate any of
    its obligations under, or result in the acceleration of any obligation
    under, any indenture, mortgage, deed of trust, voting trust agreement, loan
    agreement, bond, debenture, note agreement or other evidence of
    indebtedness, lease, contract or other agreement or instrument known to such
    counsel to which the Company or any of its Subsidiaries is a party or by
    which the Company, any of its Subsidiaries, or any of their respective
    properties is bound or affected, or violate or conflict with (i) any
    judgment, ruling, decree or order known to such counsel or (ii) any statute,
    rule or regulation of any court or other governmental agency or body,
    applicable to the business or properties of the Company or any of its
    Subsidiaries.

        (x)     To such counsel's knowledge, there is no document or contract of
    a character required by the Act to be described in the Registration
    Statement or the Prospectus or to be filed as an exhibit to the Registration
    Statement which is not described or filed as required, and each description
    of such contracts and documents that is contained in the Registration
    Statement and Prospectus fairly presents in all material respects the
    information required under the Act and the Rules and Regulations.

        (xi)    The statements under the captions "Risk Factors -- Shares
    Eligible for Future Sale," "Risk Factors -- Anti-Takeover Provisions Effects
    of Issuance of Preferred Stock;" "Management --  

                                       11

 
    Company Stock Option Plans," "Certain Transactions," "Description of Capital
    Stock," and "Shares Eligible for Future Sale" in the Prospectus, insofar as
    the statements constitute a summary of documents referred to therein or
    matters of law, are accurate summaries and fairly and correctly present, in
    all material respects, the information called for with respect to such
    documents and matters (provided, however, that such counsel may rely on
    representations of the Company with respect to the factual matters contained
    in such statements, and provided further that such counsel shall state that
    nothing has come to the attention of such counsel which leads them to
    believe that such representations are not true and correct in all material
    respects).

        (xii)   The Company is not an "investment company" or an "affiliated
    person" of, or "promoter" or "principal underwriter" for, an "investment
    company," as such terms are defined in the Investment Company Act of 1940,
    as amended.

        (xiii)  To such counsel's knowledge, no holder of securities of the
    Company has rights, which have not been waived or satisfied, to require the
    registration with the Commission shares of Common Stock or other securities,
    as part of the offering contemplated hereby.

        (xiv)   The Registration Statement has become effective under the Act,
    and to the best of such counsel's knowledge, no stop order suspending the
    effectiveness of the Registration Statement has been issued and no
    proceeding for that purpose has been instituted or is pending, threatened or
    contemplated.

        (xv)    The Registration Statement and the Prospectus comply as to form
    in all material respects with the requirement of the Act and the Rules and
    Regulations (other than the financial statements, schedules and other
    financial data contained in the Registration Statement or the Prospectus, as
    to which such counsel need express no opinion).

        (xvi)   Such counsel has participated in the preparation of the
    Registration Statement and Prospectus and has no reason to believe that, as
    of the Effective Date the Registration Statement, or any amendment or
    supplement thereto, (other than the financial statements, schedules and
    other financial data contained therein, as to which such counsel need
    express no opinion) contained any untrue statement of a material fact or
    omitted to state a material fact required to be stated therein or necessary
    to make the statements therein not misleading or that the Prospectus, or any
    amendment or supplement thereto, as of its date and the Closing Date and, if
    later, the Option Closing Date, contained or contains any untrue statement
    of a material fact or omitted or omits to state a material fact necessary to
    make the statements therein, in the light of the circumstances under which
    they were made, not misleading (other than the financial statements and
    notes thereto, and the schedules and other financial data contained therein,
    as to which such counsel need express no opinion).

    In rendering such opinion, such counsel shall be limited to the laws of the
United States and the Commonwealth of Massachusetts.

    (g) You shall have received on the Closing Date, an opinion of Lappin &
Kusmer, patent counsel for the Company, dated the Closing Date and addressed to
you, as Representatives of the several Underwriters substantially to the effect
that:

        (i)     Such counsel is generally familiar with the Company's
    technology, as reflected in the United States and foreign patents and patent
    applications listed on Schedule A to such opinion (the "Patent Portfolio"),
    and in particular, with the Company's [technology], used by the Company in
    its business and the manner of their use. Such counsel has read the portions
    of the Registration Statement and the Prospectus entitled "Risk Factors --
    Patents Proprietary Technology" and "Business -- Patents and Proprietary
    Rights" (collectively, the "Intellectual Property Portions").

                                       12

 
        (ii)    The statements set forth in the Intellectual Property Portions
    referred to in (i) above with respect to the Company's patent applications,
    issued and allowed patents, and patents licensed to it are, to the best of
    such counsel's knowledge, accurate in all material respects to the extent
    reflected in the Patent Portfolio;

        (iii)   To such counsel's best knowledge, the patent applications listed
    in the Patent Portfolio (the "Applications") have been properly prepared and
    filed on behalf of the Company and are being diligently pursued by the
    Company, the inventions described in the applications are assigned or
    licensed to the Company and no other entity or individual has any rights or
    claim in any of the inventions, Applications or any patents to be issued
    therefrom.

        (iv)    To such counsel's best knowledge, there is no pending judicial
    or governmental proceedings relating to any of the patents or patent
    applications in the Patent Portfolio or any other proprietary information to
    which the Company or any Subsidiary is a party of which any property (such
    term "property" specifically to include rights pursuant to licenses or
    options or other rights to acquire licenses) of the Company or any
    Subsidiary is subject, and to such counsel's best knowledge no such
    proceedings are threatened or contemplated by governmental authorities or
    others, and such counsel is not aware of any pending or threatened action,
    suit, or claim by others that the Company is infringing or otherwise
    violating any patent rights of others, nor is such counsel aware of any
    rights of third parties to, or infringement of, any of the Company's
    inventions described in the Applications, issued, approved, or licensed
    patents or any trademarks, trade secrets, know-how, or other proprietary
    rights of the Company which might have a material adverse effect on the
    ability of the Company to conduct its business as described in the
    Prospectus.

        (v)     Except as disclosed in the Prospectus, to such counsel's
    knowledge, there is no pending or threatened proceeding or claim that the
    manufacture, use or sale of any products, device, instrument, or other
    material made or used according to the patents or patent applications of the
    Patent Portfolio is an infringement of any valid United States or foreign
    patent held by another or a violation of any trade secret rights of another,
    nor has such counsel in the course of representing the Company has not
    concluded that any patent or trade secret of any third party would be
    infringed or violated by such acts;

        (vi)    The statements contained in the Registration Statement and the
    Prospectus, insofar as such statements constitute a summary of the Company's
    patents, foreign patents, applications, and foreign applications and
    proprietary technology, are in all material respects accurate summaries and
    fairly summarize in all material respects the legal matters, documents, and
    proceedings relating thereto;

        (vii)   Such counsel does not know of any contracts or other documents
    relating to patents or proprietary information of a character required to be
    filed as exhibits to the Registration Statement or the Prospectus or
    required to the described in the Registration Statement or the Prospectus
    that are not filed or described as required.

     (h) The Representatives shall have received an opinion, dated the Closing
Date and the Option Closing Date, from Testa, Hurwitz & Thibeault, LLP, counsel
to the Underwriters, with respect to the Registration Statement, the Prospectus
and this Agreement, which opinion shall be satisfactory in all respects to the
Representatives.
                 
     (i) Concurrently with the execution and delivery of this Agreement, the
Accountants shall have furnished to the Representatives a letter, dated the date
of its delivery, addressed to the Representatives and in form and substance
satisfactory to the Representatives, confirming that they are independent
accountants with respect to the Company and its Subsidiaries as required by the
Act and the Rules and Regulations and with respect to certain financial and
other statistical and numerical information contained in the Registration
Statement.  At the Closing Date and, as to the Option Shares, the Option Closing
Date, the Accountants shall have furnished to the Representatives a letter,
dated the date of its delivery, which shall confirm, on the basis of a review in
accordance with the procedures set forth in the letter from the Accountants,
that nothing has come to their attention during the period from the date of the
letter referred to in the 

                                       13

 
prior sentence to a date (specified in the letter) not more than five days prior
to the Closing Date and the Option Closing Date, as the case may be, which would
require any change in their letter dated the date hereof if it were required to
be dated and delivered at the Closing Date and the Option Closing Date.
                
     (j) Concurrently with the execution and delivery of this Agreement and at
the Closing Date and, as to the Option Shares, the Option Closing Date, there
shall be furnished to the Representatives a certificate, dated the date of its
delivery, signed by each of the Chief Executive Officer and the Chief Financial
Officer of the Company, in form and substance satisfactory to the
Representatives, to the effect that:

         (i)     Each signer of such certificate has carefully examined the
     Registration Statement and the Prospectus and (A) as of the date of such
     certificate, such documents are true and correct in all material respects
     and do not omit to state a material fact required to be stated therein or
     necessary in order to make the statements therein not untrue or misleading
     and (B) in the case of the certificate delivered at the Closing Date and
     the Option Closing Date, since the Effective Date no event has occurred as
     a result of which it is necessary to amend or supplement the Prospectus in
     order to make the statements therein not untrue or misleading.

         (ii)    Each of the representations and warranties of the Company
     contained in this Agreement were, when originally made, and are, at the
     time such certificate is delivered, true and correct.

         (iii)  Each of the covenants required to be performed by the Company
     herein on or prior to the date of such certificate has been duly, timely
     and fully performed and each condition herein required to be satisfied or
     fulfilled on or prior to the date of such certificate has been duly, timely
     and fully satisfied or fulfilled.

     (k)  On or prior to the Closing Date, the Representatives shall have
received the executed agreements referred to in Section 4(o).

     (l) The Shares shall be qualified for sale in such jurisdictions as the
Representatives may reasonably request and each such qualification shall be in
effect and not subject to any stop order or other proceeding on the Closing Date
or the Option Closing Date.

     (m) Prior to the Closing Date, the Shares shall have been duly authorized
for listing on the NNM upon official notice of issuance. 

     (n) The Company shall have furnished to the Representatives such
certificates, in addition to those specifically mentioned herein, as the
Representatives may have reasonably requested as to the accuracy and
completeness at the Closing Date and the Option Closing Date of any statement in
the Registration Statement or the Prospectus, as to the accuracy at the Closing
Date and the Option Closing Date of the representations and warranties of the
Company herein, as to the performance by the Company of its obligations
hereunder, or as to the fulfillment of the conditions concurrent and precedent
to the obligations hereunder of the Representatives.

     6.  Indemnification.

     (a) The Company will indemnify and hold harmless each Underwriter, the
directors, officers, employees and agents of each Underwriter and each person,
if any, who controls each Underwriter within the meaning of Section 15 of the
Act or Section 20 of the Exchange Act, from and against any and all losses,
claims, liabilities, expenses and damages (including any and all investigative,
legal and other expenses reasonably incurred in connection with, and any amount
paid in settlement of, any action, suit or proceeding or any claim asserted), to
which they, or any of them, may become subject under the Act, the Exchange Act
or other Federal or state statutory law or regulation, at common law or
otherwise, insofar as such losses, claims, liabilities, expenses or damages
arise out of or are based on any untrue statement or alleged untrue statement of
a material fact contained in any preliminary prospectus, the Registration
Statement or the Prospectus or any amendment or supplement to the Registration
Statement or the Prospectus, or the

                                       14

 
omission or alleged omission to state in such document a material fact required
to be stated in it or necessary to make the statements in it not misleading in
the light of the circumstances in which they were made, or arise out of or are
based in whole or in part on any inaccuracy in the representations and
warranties of the Company contained herein or any failure of the Company to
perform its obligations hereunder or under law in connection with the
transactions contemplated hereby; provided, however, that (i) the Company will
not be liable to the extent that such loss, claim, liability, expense or damage
arises out of or is based upon the sale of the Shares in the public offering to
any person by an Underwriter and arises out of or is based on an untrue
statement or omission or alleged untrue statement or omission made in reliance
on and in conformity with information relating to any Underwriter furnished in
writing to the Company by the Representatives, on behalf of any Underwriter,
expressly for inclusion in the Registration Statement, the preliminary
prospectus or the Prospectus, or any amendment or supplement thereto, and (ii)
the Company will not be liable to any Underwriter, the directors, officers,
employees or agents of such Underwriter or any person controlling such
Underwriter with respect to any loss, claim, liability, expense, or damage
arising out of or based on any untrue statement or omission or alleged untrue
statement or omission or alleged omission to state a material fact in the
preliminary prospectus which is corrected in the Prospectus if the person
asserting any such loss, claim, liability, charge or damage purchased Shares
from such Underwriter but was not sent or given a copy of the Prospectus at or
prior to the written confirmation of the sale of such Shares to such person. The
Company acknowledges that the statements set forth under the heading
"Underwriting" and "Underwriting Discounts and Commissions" in the preliminary
prospectus and the Prospectus, or any amendment or supplement thereto,
constitute the only information relating to any Underwriter furnished in writing
to the Company by the Representatives on behalf of the Underwriters expressly
for inclusion in the Registration Statement, the preliminary prospectus or the
Prospectus. This indemnity agreement will be in addition to any liability that
the Company might otherwise have.

     (b) Each Underwriter will indemnify and hold harmless the Company, each
director of the Company, each officer of the Company who signs the Registration
Statement, and each person, if any, who controls the Company within the meaning
of Section 15 of the Act or Section 20 of the Exchange Act, to the same extent
as the foregoing indemnity from the Company to each Underwriter, as set forth in
Section 6(a), but only insofar as losses, claims, liabilities, expenses or
damages arise out of or are based on any untrue statement or omission or alleged
untrue statement or omission made in reliance on and in conformity with
information relating to any Underwriter furnished in writing to the Company by
the Representatives, on behalf of such Underwriter, expressly for use in the
Registration Statement, the preliminary prospectus or the Prospectus, or any
amendment or supplement thereto.  The Company acknowledges that the statements
set forth under the heading "Underwriting" in the preliminary prospectus and the
Prospectus, or any amendment or supplement thereto, constitute the only
information relating to any Underwriter furnished in writing to the Company by
the Representatives on behalf of the Underwriters expressly for inclusion in the
Registration Statement, the preliminary prospectus or the Prospectus, or any
amendment or supplement thereto.  This indemnity will be in addition to any
liability that each Underwriter might otherwise have.

     (c) Any party that proposes to assert the right to be indemnified under
this Section 6 shall, promptly after receipt of notice of commencement of any
action against such party in respect of which a claim is to be made against an
indemnifying party or parties under this Section 6, notify each such
indemnifying party in writing of the commencement of such action, enclosing with
such notice a copy of all papers served, but the omission so to notify such
indemnifying party will not relieve it from any liability that it may have to
any indemnified party under the foregoing provisions of this Section 6 unless,
and only to the extent that, such omission results in the loss of substantive
rights or defenses by the indemnifying party. If any such action is brought
against any indemnified party and it notifies the indemnifying party of its
commencement, the indemnifying party will be entitled to participate in and, to
the extent that it elects by delivering written notice to the indemnified party
promptly after receiving notice of the commencement of the action from the
indemnified party, jointly with any other indemnifying party similarly notified,
to assume the defense of the action, with counsel reasonably satisfactory to the
indemnified party. After notice from the indemnifying party to the indemnified
party of its election to assume the defense, the indemnifying party will not be
liable to the indemnified party for any legal or other expenses except as
provided below and except for the reasonable costs of investigation subsequently
incurred by the indemnified party in connection with the defense. The
indemnified party will have the right to employ its own counsel in any such
action, but the fees, expenses and other charges of such counsel will be at the
expense of such indemnified party unless (i) the employment of counsel by the
indemnified party has been authorized in writing by the indemnifying party, (ii)
the indemnified party has reasonably concluded (based on 

                                       15

 
advice of counsel) that there may be legal defenses available to it or other
indemnified parties that are different from or in addition to those available to
the indemnifying party, (iii) a conflict or potential conflict exists (based on
advice of counsel to the indemnified party) between the indemnified party and
the indemnifying party (in which case the indemnifying party will not have the
right to direct the defense of such action on behalf of the indemnified party)
or (iv) the indemnifying party has not in fact employed counsel to assume the
defense of such action within a reasonable time after receiving notice of the
commencement of the action, in each of which cases the reasonable fees,
disbursements and other charges of counsel will be at the expense of the
indemnifying party or parties. It is understood that the indemnifying party or
parties shall not, in connection with any proceeding or related proceedings in
the same jurisdiction, be liable for the reasonable fees, disbursements and
other charges of more than one separate firm admitted to practice in such
jurisdiction at any one time for all such indemnified party or parties. All such
fees, disbursements and other charges will be reimbursed by the indemnifying
party promptly as they are incurred. Any indemnifying party will not be liable
for any settlement of any action or claim effected without its written consent
(which consent will not be unreasonably withheld).

     (d) If the indemnification provided for in this Section 6 is applicable in
accordance with its terms but for any reason is held to be unavailable to or
insufficient to hold harmless an indemnified party under paragraphs (a), (b) and
(c) of this Section 6 in respect of any losses, claims, liabilities, expenses
and damages referred to therein, then each applicable indemnifying party, in
lieu of indemnifying such indemnified party, shall contribute to the amount paid
or payable (including any investigative, legal and other expenses reasonably
incurred in connection with, and any amount paid in settlement of, any action,
suit or proceeding or any claim asserted, but after deducting any contribution
received by the Company from persons other than the Underwriters, such as
persons who control the Company within the meaning of the Act, officers of the
Company who signed the Registration Statement and directors of the Company, who
also may be liable for contribution) by such indemnified party as a result of
such losses, claims, liabilities, expenses and damages in such proportion as
shall be appropriate to reflect the relative benefits received by the Company,
on the one hand, and the Underwriters, on the other hand.  The relative benefits
received by the Company, on the one hand, and the Underwriters, on the other
hand, shall be deemed to be in the same proportion as the total net proceeds
from the offering (before deducting expenses) received by the Company bear to
the total underwriting discounts and commissions received by the Underwriters,
in each case as set forth in the table on the cover page of the Prospectus.  If,
but only if, the allocation provided by the foregoing sentence is not permitted
by applicable law, the allocation of contribution shall be made in such
proportion as is appropriate to reflect not only the relative benefits referred
to in the foregoing sentence but also the relative fault of the Company, on the
one hand, and the Underwriters, on the other hand, with respect to the
statements or omissions which resulted in such loss, claim, liability, expense
or damage, or action in respect thereof, as well as any other relevant equitable
considerations with respect to such offering.  Such relative fault shall be
determined by reference to whether the untrue or alleged untrue statement of a
material fact or omission or alleged omission to state a material fact relates
to information supplied by the Company or the Representatives on behalf of the
Underwriters, the intent of the parties and their relative knowledge, access to
information and opportunity to correct or prevent such statement or omission.
The Company and the Underwriters agree that it would not be just and equitable
if contributions pursuant to this Section 6(d) were to be determined by pro rata
allocation (even if the Underwriters were treated as one entity for such
purpose) or by any other method of allocation which does not take into account
the equitable considerations referred to herein.  The amount paid or payable by
an indemnified party as a result of the loss claim, liability, expense or
damage, or action in respect thereof, referred to above in this Section 6(d)
shall be deemed to include, for purposes of this Section 6(d), any legal or
other expenses reasonably incurred by such indemnified party in connection with
investigating or defending any such action or claim.  Notwithstanding the
provisions of this Section 6(d), no Underwriter shall be required to contribute
any amount in excess of the underwriting discounts received by it and no person
found guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Act) will be entitled to contribution from any person who was not
guilty of such fraudulent misrepresentation.  The Underwriters' obligations to
contribute as provided in this Section 6(d) are several in proportion to their
respective underwriting obligations and not joint.  For purposes of this Section
6(d), any person who controls a party to this Agreement within the meaning of
the Act will have the same rights to contribution as that party, and each
officer of the Company who signed the Registration Statement will have the same
rights to contribution as the Company, subject in each case to the provisions
hereof.  Any party entitled to contribution, promptly after receipt of notice of
commencement of any action against any such party in respect of which a claim
for contribution may be made under this Section 6(d), will notify any such party
or parties from whom contribution may be sought, but the omission 

                                       16

 
so to notify will not relieve the party or parties from whom contribution may be
sought from any other obligation it or they may have under this Section 6(d). No
party will be liable for contribution with respect to any action or claim
settled without its written consent (which consent will not be unreasonably
withheld).

     (e) The indemnity and contribution agreements contained in this Section 6
and the representations and warranties of the Company contained in this
Agreement shall remain operative and in full force and effect regardless of (i)
any investigation made by or on behalf of the Underwriters, (ii) acceptance of
any of the Shares and payment therefor or (iii) any termination of this
Agreement.

     7.  Reimbursement of Certain Expenses. In addition to its other obligations
under Section 6(a) of this Agreement, the Company hereby agrees to reimburse on
a quarterly basis the Underwriters for all reasonable legal and other expenses
incurred in connection with investigating or defending any claim, action,
investigation, inquiry or other proceeding arising out of or based upon, in
whole or in part, any statement or omission or alleged statement or omission, or
any inaccuracy in the representations and warranties of the Company contained
herein or failure of the Company to perform its or their respective obligations
hereunder or under law, all as described in Section 6(a), notwithstanding the
absence of a judicial determination as to the propriety and enforceability of
the obligations under this Section 7 and the possibility that such payment might
later be held to be improper; provided, however, that, to the extent any such
payment is ultimately held to be improper, the persons receiving such payments
shall promptly refund them.

     8.  Termination.  The obligations of the several Underwriters under this
Agreement may be terminated at any time on or prior to the Closing Date (or,
with respect to the Option Shares, on or prior to the Option Closing Date), by
notice to the Company from the Representatives, without liability on the part of
any Underwriter to the Company if, prior to delivery and payment for the Firm
Shares or Option Shares, as the case may be, in the reasonable judgment
of the Representatives, (i) trading in any of the equity securities of the
Company shall have been suspended by the Commission or by The Nasdaq National
Stock Market, (ii) trading in securities generally on The Nasdaq National Stock
Market  shall have been suspended or limited or minimum or maximum prices shall
have been generally established on such exchange, or additional material
governmental restrictions, not in force on the date of this Agreement, shall
have been imposed upon trading in securities generally by such exchange or by
order of the Commission or any court or other governmental authority, (iii) a
general banking moratorium shall have been declared by either Federal or  New
York State authorities or (iv) any material adverse change in the financial or
securities markets in the United States or in political, financial or economic
conditions in the United States or any outbreak or material escalation of
hostilities or other calamity or crisis shall have occurred, the effect of which
is such as to make it, in the sole judgment of the Representatives,
impracticable or inadvisable to proceed with completion of the public offering
or the delivery of and payment for the Shares.

    If this Agreement is terminated pursuant to Section 9 hereof, the Company
shall have no liability to any Underwriter except as provided in Sections 4(j),
7 and 8 hereof; but, if for any other reason the purchase of the Shares by the
Underwriters is not consummated or if for any reason the Company shall be unable
to perform its obligations hereunder, the Company will reimburse the several
Underwriters for all out-of-pocket expenses (including the fees, disbursements
and other charges of counsel to the Underwriters) incurred by them in connection
with the offering of the Shares.

     9.  Substitution of Underwriters. If any one or more of the Underwriters
shall fail or refuse to purchase any of the Firm Shares which it or they have
agreed to purchase hereunder, and the aggregate number of Firm Shares which such
defaulting Underwriter or Underwriters agreed but failed or refused to purchase
is not more than one-tenth of the aggregate number of Firm Shares, the other
Underwriters shall be obligated, severally, to purchase the Firm Shares which
such defaulting Underwriter or Underwriters agreed but failed or refused to
purchase, in the proportions which the number of Firm Shares which they have
respectively agreed to purchase pursuant to Section 1 bears to the aggregate
number of Firm Shares which all such non-defaulting Underwriters have so agreed
to purchase, or in such other proportions as the Representatives may specify;
provided that in no event shall the maximum number of Firm Shares which any
Underwriter has become obligated to purchase pursuant to Section 1 be increased
pursuant to this Section 10 by more than one-ninth of such number of Firm Shares
without the prior written consent of such Underwriter. If any  

                                       17

 
Underwriter or Underwriters shall fail or refuse to purchase any Firm Shares and
the aggregate number of Firm Shares which such defaulting Underwriter or
Underwriters agreed but failed or refused to purchase exceeds one-tenth of the
aggregate number of the Firm Shares and arrangements satisfactory to the
Representatives and the Company for the purchase of such Firm Shares are not
made within 48 hours after such default, this Agreement will terminate without
liability on the part of any non-defaulting Underwriter and the Company for the
purchase or sale of any Shares under this Agreement. In any such case either the
Representatives or the Company shall have the right to postpone the Closing
Date, but in no event for longer than seven days, in order that the required
changes, if any, in the Registration Statement and the Prospectus or in any
other documents or arrangements may be effected. Any action taken pursuant to
this Section 10 shall not relieve any defaulting Underwriter from liability in
respect of any default of such Underwriter under this Agreement.

     10. Miscellaneous.  Notice given pursuant to any of the provisions of this
Agreement shall be in writing and, unless otherwise specified, shall be mailed
or delivered (a) if to the Company, at the office of the Company, Photoelectron
Corporation, 5 Forbes Road, Lexington, Massachusetts 02173, Attention: Chief
Executive Officer, with a copy to Daniel Avery, Esquire, Goulston & Storrs,
P.C., 400 Atlantic Avenue, Boston, Massachusetts 02110, or (b) if to the
Underwriters, to the Representatives at the offices of Needham & Company, Inc.,
445 Park Avenue, New York, New York 10022, Attention: Corporate Finance
Department, with a copy to Edwin L. Miller, Jr., Esquire, Testa, Hurwitz &
Thibeault, LLP, 125 High Street, Boston, Massachusetts 02110.  Any such notice
shall be effective only upon receipt.  Any notice under such Section 8 or 9 may
be made by telex or telephone, but if so made shall be subsequently confirmed in
writing.

    This Agreement has been and is made solely for the benefit of the several
Underwriters, the Company, and the controlling persons, directors and officers
referred to in Section 6, and their respective successors and assigns, and no
other person shall acquire or have any right under or by virtue of this
Agreement.  The term "successors and assigns" as used in this Agreement shall
not include a purchaser, as such purchaser, of Shares from any of the several
Underwriters.

    Any action required or permitted to be made by the Representatives under
this Agreement may be taken by them jointly or by Needham & Company, Inc.

    This Agreement shall be governed by and construed in accordance with the
laws of the State of New York applicable to contracts made and to be performed
entirely within such State.

    This Agreement may be signed in two or more counterparts with the same
effect as if the signatures thereto and hereto were upon the same instrument.

    In case any provision in this Agreement shall be invalid, illegal or
unenforceable, the validity, legality and enforceability of the remaining
provisions shall not in any way be affected or impaired thereby.

    The Company and the Underwriters each hereby waive any right they may have
to a trial by jury in respect of any claim based upon or arising out of this
Agreement or the transactions contemplated hereby.

                                       18

 
    Please confirm that the foregoing correctly sets forth the agreement among
the Company and the several Underwriters.

                                 Very truly yours,

                                 Photoelectron Corporation


                                 By:  
                                    ----------------------------    
                                     Title:



Confirmed as of the date first
above mentioned:

Needham & Company, Inc.
Dain Bosworth Incorporated
   Acting on behalf of themselves
   and as the Representatives of
   the other several Underwriters
   named in Schedule I hereto.


By: NEEDHAM & COMPANY, INC.


By:                           
   ---------------------------  
   Title:

                                       19

 
                                  SCHEDULE I

                                 UNDERWRITERS


                                                       Number of
                                                          Firm
                                                         Shares
Underwriters                                         to be Purchased
- ------------                                         ---------------

Needham & Company, Inc..............................
Dain Bosworth Incorporated..........................



                                                         ________
      Total.........................................       
                                                         ========
                                       20

 
                                  SCHEDULE II

                           FORM OF LOCK-UP AGREEMENT
                   [AND DIRECTORS, OFFICERS AND STOCKHOLDERS
                 OF THE COMPANY WHO SHALL SIGN SUCH AGREEMENT]



    The undersigned is a holder of securities of [Issuer Name], a ______
corporation (the "Company"), and wishes to facilitate the public offering of
shares of the Common Stock (the "Common Stock") of the Company (the "Offering").
The undersigned recognizes that such Offering will be of benefit to the
undersigned.

    In consideration of the foregoing and in order to induce you to act as
underwriters in connection with the Offering, the undersigned hereby agrees that
he, she or it will not, without the prior written approval of Needham & Company,
Inc., acting on its own behalf and/or on behalf of other representatives of the
underwriters, directly or indirectly, sell, contract to sell, make any short
sale, pledge, or otherwise dispose of, or enter into any hedging transaction
that is likely to result in a transfer of, any shares of Common Stock, options
to acquire shares of Common Stock or securities exchangeable for or convertible
into shares of Common Stock of the Company which he, she or it may own,
[exclusive of any shares of Common Stock purchased in connection with the
Company's public offering [or purchased in the public trading market]], for a
period commencing as of the date hereof and ending on the date which is [one
hundred eighty (180)] days after the date of the final Prospectus relating to
the Offering[; provided, however, that the foregoing shall not prohibit any
distribution by a partnership to its partners so long as such partners agree to
be bound by the terms of this Agreement].  The undersigned confirms that he, she
or it understands that the underwriters and the Company will rely upon the
representations set forth in this Agreement in proceeding with the Offering.
The undersigned further confirms that the agreements of the undersigned are
irrevocable and shall be binding upon the undersigned's heirs, legal
representatives, successors and assigns.  The undersigned agrees and consents to
the entry of stop transfer instructions with the Company's transfer agent
against the transfer of securities held by the undersigned except in compliance
with this Agreement.

    This Agreement shall be binding on the undersigned and his, her or its
respective successors, heirs, personal representatives and assigns.
 

                                               ___________________________

                                       21