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                                                                      Exhibit 99


                                PROMISSORY NOTE


$135,000,000                                                  New York, New York
                                                                    May 28, 1999



          FOR VALUE RECEIVED, EG&G, INC., a corporation organized and existing
under the laws of Massachusetts (the "COMPANY"), by this promissory note (this
"NOTE") unconditionally promises to pay to the order of THE PERKIN-ELMER
CORPORATION, a corporation organized and existing under the laws of New York
(the "SELLER"), the principal sum of ONE HUNDRED THIRTY-FIVE MILLION DOLLARS
($135,000,000) on May 25, 2000.

          The Company further promises to pay interest to the Seller on the
unpaid principal amount hereof from the date hereof until maturity (whether as
stated, by acceleration or otherwise) at a rate per annum equal to 5%. Interest
is payable quarterly in arrears on the last Business Day of August, November and
February and at the maturity hereof (whether as stated, by acceleration or
otherwise). Any principal, interest or any other amount hereunder which is not
paid when due (whether as stated, by acceleration or otherwise) shall, to the
extent permitted by law, thereafter bear interest at a rate per annum equal to
7% until payment in full thereof, as well after as before judgment. Interest,
principal and any other amount due hereunder shall be payable on demand in
respect of any past due amount and upon payment in full of this Note. For
purposes hereof: "BUSINESS DAY" shall mean a day other than a Saturday, Sunday
or other day on which commercial banks in New York City are authorized or
required by law to close; "CREDIT AGREEMENT" shall mean the Credit Agreement,
dated as of March 5, 1999, by and among the Company, the lenders parties
thereto, The Chase Manhattan Bank, as administrative agent, and Chase Securities
Inc., as advisor and lead arranger, as such Agreement may be amended,
supplemented or otherwise modified from time to time, including any agreement
refinancing, replacing or otherwise restructuring all or any portion of the
indebtedness under such agreement and whether with the same, or any other agent,
lender or group of lenders; "GUARANTEE AND COLLATERAL AGREEMENT" shall mean the
Guarantee and Collateral Agreement, dated as of the date hereof, made by the
Company and the other grantors that are signatories thereto in favor of the
Seller; "LOAN DOCUMENTS" shall mean the collective reference to this Note, the
Guarantee and Collateral Agreement and the Promissory Note, dated as of the date
hereof, made by the Company in favor of the Seller, in the principal amount of
$15,000,000; and "LOAN PARTIES" shall mean the collective reference to the
Company and each other party to the Loan Documents.

          The Company shall have the right to prepay this Note at any time and
from time to time, in whole or in part, provided that the minimum amount of each
partial prepayment shall be $1,000,000.

          All payments to be made hereunder by the Company shall be made without
set-off or counterclaim, in immediately available funds by wire transfer to the
account of the Seller in accordance with the following instructions:


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          Bank: Citibank, N.A., New York, NY
          Swift Code: Citi US 33
          ABA #: 021 0000 89
          Account #: 000-42657
          Credit: The Perkin Elmer Corporation

Whenever any payment hereunder shall be stated to be due on a day which is not a
Business Day, such payment shall be made on the next succeeding Business Day.

          The Company hereby waives diligence, demand, presentment, protest and
notice of any kind, and assents to extensions of the time of payment, release,
surrender or substitution of security, or forbearance or other indulgence,
without notice.

          This Note may not be changed, modified or terminated orally, but only
by an agreement in writing signed by both parties.

          The Company agrees to pay all of the Seller's costs and out-of-pocket
expenses (including, without limitation, fees and disbursements of counsel)
arising in connection with the enforcement of, and preservation of rights under,
this Note and the other Loan Document in the case that the Company shall have
failed to comply with its obligations under this Note or the other Loan Document
and such failure shall be continuing.

          If (a) the Company shall fail to pay when due interest on this Note
and such failure shall have continued for a period of three Business Days; (b)
any representation or warranty made by any Loan Party in any Loan Document shall
prove to have been false or misleading in any material respect as of the time
when made or deemed made; (c) any Loan Party shall default in the performance or
observance of (i) any covenant contained in Section 5.3 of the Guarantee and
Collateral Agreement or (ii) any other covenant in the Guarantee and Collateral
Agreement and such default shall continue unremedied for a period of 10 days
after notice thereof from the Seller to the Company; (d) a "Change of Control"
as defined in the Credit Agreement (as in effect on the date hereof without
giving effect to any future amendments, supplements or other modifications
thereto) shall occur; (e) an "Event of Default" as defined in the Credit
Agreement shall have occurred (each of the foregoing, an "EVENT OF DEFAULT"),
the Seller may, by notice of default given to the Company, declare all unpaid
principal, accrued interest and all other amounts payable under this Note to be
immediately due and payable without presentment, demand, protest or other notice
of any kind, each of which is hereby expressly waived by the Company.

          No action or omission by the Seller shall constitute a waiver of any
rights or remedies of the Seller hereunder. Such rights and remedies are
cumulative and not exclusive of any rights or remedies provided by law. Payment
of principal of and interest on this Note shall not discharge the Company's
obligation with respect to any other amount payable hereunder. This Note shall
be binding upon and inure to the benefit of the Company, the Seller and their
respective successors and assigns, except that the Company may not assign or
transfer any of its rights or obligations under this Note without the prior
written consent of the Seller.


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          THIS NOTE SHALL BE A CONTRACT UNDER, AND BE GOVERNED BY, AND CONSTRUED
AND INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.


                                             EG&G, INC.



                                             By:  /s/ Gregory L. Summe
                                                ---------------------------
                                                Name:
                                                Title:



                                             Address for Notices:

                                             45 William Street
                                             Wellesley, MA 02181
                                             Attention: Treasurer
                                             Telecopy: (781) 431-4113