EXHIBIT 3.1

                               HALE AND DORR LLP
                               COUNSELORS AT LAW

                                  HALEDORR.COM
                       60 STATE STREET - BOSTON, MA 02109
                         617-526-6000 - FAX 617-526-5000

                                                      January 14, 2004

Hybridon, Inc.
345 Vassar Street
Cambridge, MA 02139

         Re: Registration Statement on Form S-3

Ladies and Gentlemen:

         This opinion is furnished to you in connection with the Registration
Statement on Form S-3 (the "Registration Statement") being filed, on the date
hereof, by Hybridon, Inc., a Delaware corporation (the "Company"), with the
Securities and Exchange Commission (the "Commission") under the Securities Act
of 1933, as amended (the "Securities Act"), with respect to the Company's:

         1. common stock, $0.001 par value per share (the "Common Stock"); and

         2. warrants to purchase Common Stock (the "Warrants," and, together
with the Common Stock, the "Securities");

all of which may be issued from time to time on a delayed or continuous basis
pursuant to Rule 415 under the Securities Act. The total number of shares of
Common Stock that the Company may issue directly and that the Company may issue
upon exercise of the Warrants issued pursuant to the Registration Statement will
not exceed 20,000,000.

         The Warrants may be issued pursuant to a warrant agreement between the
Company and a bank or trust company as a warrant agent or pursuant to warrant
agreements with the purchasers of the Warrants.

         We are acting as counsel for the Company in connection with the filing
of the Registration Statement and have examined the Registration Statement
including the exhibits thereto. We have also examined and relied upon minutes of
meetings of the Board of Directors of the Company as provided to us by the
Company, the Certificate of Incorporation and By-Laws of the Company, each as
restated and/or amended to date, and such other documents, corporate records,
instruments, laws and regulations as we have deemed necessary for purposes of
rendering the opinions hereinafter set forth.

         In our examination of the foregoing documents, we have assumed the
genuineness of all signatures, the authenticity of all documents submitted to us
as originals, the conformity to original documents of all documents submitted to
us as copies, the authenticity of the originals of such latter documents and the
legal capacity of all signatories to such documents who are natural persons.
Insofar as this opinion relates to factual matters, we have assumed with your



BOSTON       LONDON      MUNICH      NEW YORK      OXFORD      PRINCETON      RESTON       WALTHAM       WASHINGTON
- -------------------------------------------------------------------------------------------------------------------
                                                                                 


       Hale and Dorr LLP is a Massachusetts Limited Liability Partnership



Hybridon, Inc.
January 14, 2004
Page 2

permission and without independent investigation that the statements of the
Company contained in the Registration Statement are true and correct as to all
factual matters stated therein.

         We assume that the appropriate action will be taken, prior to the offer
and sale of the Securities, to register and qualify the Securities for sale
under all applicable state securities or "blue sky" laws.

         We express no opinion herein as to the laws of any state or
jurisdiction other than the state laws of the Commonwealth of Massachusetts, the
General Corporation Law of the State of Delaware and the federal laws of the
United States of America.

         Based upon and subject to the foregoing, we are of the opinion that:

         1. With respect to the Common Stock, when (i) specifically authorized
for issuance by the Company's Board of Directors or an authorized committee
thereof (the "Authorizing Votes"), (ii) the Registration Statement has become
effective under the Securities Act, (iii) the terms of the issuance and sale of
the Common Stock have been duly established in conformity with the Company's
Certificate of Incorporation and By-laws and do not violate any applicable law
or result in a default under or breach of any agreement or instrument binding
upon the Company and comply with any and all requirements or restrictions
imposed by any court or governmental body having jurisdiction over the Company,
(iv) the Common Stock has been issued and sold as contemplated by the
Registration Statement, and (v) the Company has received the consideration
provided for in the Authorizing Votes and such consideration per share is not
less than the par value per share of the Common Stock, the Common Stock will be
validly issued, fully paid and non-assessable.

         2. With respect to the Warrants, when (i) specifically authorized for
issuance by the Authorizing Votes, (ii) the Registration Statement has become
effective under the Securities Act, (iii) the warrant agreement or agreements
relating to the Warrants have been duly authorized, executed, and delivered,
(iv) the terms of the Warrants and of their issuance and sale have been duly
established in conformity with the warrant agreement or agreements relating to
the Warrants and do not violate any applicable law or result in a default under
or breach of any agreement or instrument binding upon the Company and comply
with any and all requirements or restrictions imposed by any court or
governmental body having jurisdiction over the Company, (v) the Warrants, if
separate and apart from the warrant agreement or agreements, have been duly
executed and countersigned in accordance with the warrant agreement or
agreements relating to the Warrants, (vi) the Warrants have been issued and sold
as contemplated by the Registration Statement, and (vii) the Company has
received the consideration provided for in the Authorizing Votes, such Warrants
will constitute valid and legally binding obligations of the Company, subject to
bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and
similar laws of general applicability relating to or affecting creditors' rights
and to general equity principles.

         It is understood that this opinion is to be used only in connection
with the offer and sale of the Securities while the Registration Statement is in
effect.



Hybridon, Inc.
January 14, 2004
Page 3

         Please note that we are opining only as to the matters expressly set
forth herein, and no opinion should be inferred as to any other matters. This
opinion is based upon currently existing statutes, rules, regulations and
judicial decisions, and we disclaim any obligation to advise you of any change
in any of these sources of law or subsequent legal or factual developments which
might affect any matters or opinions set forth herein.

         We hereby consent to the filing of this opinion with the Commission as
an exhibit to the Registration Statement in accordance with the requirements of
Item 601(b)(5) of Regulation S-K under the Securities Act and to the use of our
name therein and in the related Prospectus under the caption "Legal Matters." In
giving such consent, we do not hereby admit that we are in the category of
persons whose consent is required under Section 7 of the Securities Act or the
rules and regulations of the Commission.

                                       Very truly yours,

                                       /s/ Hale and Dorr LLP

                                       Hale and Dorr LLP