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                                                               EXHIBIT 3.1

 
                          CERTIFICATE OF INCORPORATION
                                       OF
                  INHALE THERAPEUTIC SYSTEMS (DELAWARE), INC.
 
    The undersigned, a natural person (the "Sole Incorporator"), for the purpose
of organizing a corporation to conduct the business and promote the purposes
hereinafter stated, under the provisions and subject to the requirements of the
laws of the State of Delaware hereby certifies that:
 
                                       I.
 
    The name of this corporation is Inhale Therapeutic Systems (Delaware), Inc.
 
                                      II.
 
    The address of the registered office of the corporation in the State of
Delaware is 1209 Orange St., City of Wilmington, County of New Castle, and the
name of the registered agent of the corporation in the State Delaware at such
address is CT Corporation.
 
                                      III.
 
    The purpose of this corporation is to engage in any lawful act or activity
for which a corporation may be organized under the General Corporation Law of
the State of Delaware.
 
                                      IV.

    A.  This corporation is authorized to issue two classes of stock to be 
designated, respectively, "Common Stock" and "Preferred Stock." The total 
number of shares which the corporation is authorized to issue is sixty 
million (60,000,000) shares. Fifty million (50,000,000) shares shall be 
Common Stock, each having a par value of one-hundredth of one cent ($.0001). 
Ten million (10,000,000) shares shall be Preferred Stock, each having a par 
value of one-hundredth of one cent ($.0001).

    B.  The Preferred Stock may be issued from time to time in one or more
series. The Board of Directors is hereby authorized, by filing a certificate (a
"Preferred Stock Designation") pursuant to the Delaware General Corporation Law,
to fix or alter from time to time the designation, powers, preferences and
rights of the shares of each such series and the qualifications, limitations or
restrictions of any wholly unissued series of Preferred Stock, and to establish
from time to time the number of shares constituting any such series or any of
them; and to increase or decrease the number of shares of any series subsequent
to the issuance of shares of that series, but not below the number of shares of
such series then outstanding. In case the number of shares of any series shall
be decreased in accordance with the foregoing sentence, the shares constituting
such decrease shall resume the status that they had prior to the adoption of the
resolution originally fixing the number of shares of such series.
 
                                       V.
 
    For the management of the business and for the conduct of the affairs of the
corporation, and in further definition, limitation and regulation of the powers
of the corporation, of its directors and of its stockholders or any class
thereof, as the case may be, it is further provided that:
 
    A.
 
        1.  The management of the business and the conduct of the affairs of the
    corporation shall be vested in its Board of Directors. The number of
    directors which shall constitute the whole Board of Directors shall be fixed
    exclusively by one or more resolutions adopted by the Board of Directors.
 
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        2.  Subject to the rights of the holders of any series of Preferred
    Stock to elect additional directors under specified circumstances, the
    directors shall be divided into three classes designated as Class I, Class
    II and Class III, respectively. Directors shall be assigned to each class in
    accordance with a resolution or resolutions adopted by the Board of
    Directors. At the first annual meeting of stockholders following the
    adoption and filing of this Certificate of Incorporation, the term of office
    of the Class I directors shall expire and Class I directors shall be elected
    for a full term of three years. At the second annual meeting of stockholders
    following the adoption and filing of this Certificate of Incorporation, the
    term of office of the Class II directors shall expire and Class II directors
    shall be elected for a full term of three years. At the third annual meeting
    of stockholders following the adoption and filing of this Certificate of
    Incorporation, the term of office of the Class III directors shall expire
    and Class III directors shall be elected for a full term of three years. At
    each succeeding annual meeting of stockholders, directors shall be elected
    for a full term of three years to succeed the directors of the class whose
    terms expire at such annual meeting.
 
        Notwithstanding the foregoing provisions of this Article, each director
    shall serve until his successor is duly elected and qualified or until his
    death, resignation or removal. No decrease in the number of directors
    constituting the Board of Directors shall shorten the term of any incumbent
    director.
 
        3.  Subject to the rights of the holders of any series of Preferred
    Stock, no director shall be removed without cause. Subject to limitations
    imposed by law, the Board of Directors or any individual director may be
    removed from office at any time with cause by the affirmative vote of the
    holders of a majority of the voting power of all the then-outstanding shares
    of voting stock of the corporation, entitled to vote at an election of
    directors (the "Voting Stock").
 
        4.  Subject to the rights of the holders of any series of Preferred
    Stock, any vacancies on the Board of Directors resulting from death,
    resignation, disqualification, removal or other causes and any newly created
    directorships resulting from any increase in the number of directors, shall,
    unless the Board of Directors determines by resolution that any such
    vacancies or newly created directorships shall be filled by the
    stockholders, except as otherwise provided by law, be filled only by the
    affirmative vote of a majority of the directors then in office, even though
    less than a quorum of the Board of Directors, and not by the stockholders.
    Any director elected in accordance with the preceding sentence shall hold
    office for the remainder of the full term of the director for which the
    vacancy was created or occurred and until such director's successor shall
    have been elected and qualified.
 
    B.
 
        1.  Subject to paragraph (h) of Section 43 of the Bylaws, the Bylaws may
    be altered or amended or new Bylaws adopted by the affirmative vote of at
    least sixty-six and two-thirds percent (66 2/3%) of the voting power of all
    of the then-outstanding shares of the Voting Stock. The Board of Directors
    shall also have the power to adopt, amend, or repeal Bylaws.
 
        2.  The directors of the corporation need not be elected by written
    ballot unless the Bylaws so provide.
 
        3.  No action shall be taken by the stockholders of the corporation
    except at an annual or special meeting of stockholders called in accordance
    with the Bylaws.
 
        4.  Special meetings of the stockholders of the corporation may be
    called, for any purpose or purposes, by (i) the Chairman of the Board of
    Directors, (ii) the Chief Executive Officer, (iii) the Board of Directors
    pursuant to a resolution adopted by a majority of the total number of
    authorized directors (whether or not there exist any vacancies in previously
    authorized directorships at the time any such resolution is presented to the
    Board of Directors for adoption), or (iv) by the holders of the
 
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    shares entitled to cast not less than ten percent (10%) of the votes at the
    meeting, and shall be held at such place, on such date, and at such time as
    the Board of Directors shall fix.
 
        5.  Advance notice of stockholder nominations for the election of
    directors and of business to be brought by stockholders before any meeting
    of the stockholders of the corporation shall be given in the manner provided
    in the Bylaws of the corporation.
 
                                      VI.
 
    A.  A director of the corporation shall not be personally liable to the
corporation or its stockholders for monetary damages for any breach of fiduciary
duty as a director, except for liability (i) for any breach of the director's
duty of loyalty to the corporation or its stockholders, (ii) for acts or
omissions not in good faith or which involve intentional misconduct or a knowing
violation of law (iii) under Section 174 of the Delaware General Corporation
Law, or (iv) for any transaction from which the director derived an improper
personal benefit. If the Delaware General Corporation Law is amended after
approval by the stockholders of this Article to authorize corporate action
further eliminating or limiting the personal liability of directors, then the
liability of a director shall be eliminated or limited to the fullest extent
permitted by the Delaware General Corporation Law, as so amended.
 
    B.  Any repeal or modification of this Article VI shall be prospective and
shall not affect the rights under this Article VI in effect at the time of the
alleged occurrence of any act or omission to act giving rise to liability or
indemnification.
 
                                      VII.
 
    A.  The corporation reserves the right to amend, alter, change or repeal any
provision contained in this Certificate of Incorporation, in the manner now or
hereafter prescribed by statute, except as provided in paragraph B of this
Article VII, and all rights conferred upon the stockholders herein are granted
subject to this reservation.
 
    B.  Notwithstanding any other provisions of this Certificate of
Incorporation or any provision of law which might otherwise permit a lesser vote
or no vote, but in addition to any affirmative vote of the holders of any
particular class or series of the Voting Stock required by law, this Certificate
of Incorporation or any Preferred Stock Designation, the affirmative vote of the
holders of at least sixty-six and two-thirds percent (66 2/3%) of the voting
power of all of the then-outstanding shares of the Voting Stock, voting together
as a single class, shall be required to alter, amend or repeal Articles V, VI,
and VII.
 
                                     VIII.
 
    The name and the mailing address of the Sole Incorporator is as follows:
 
<TABLE>
<S>                                            <C>
         NAME                                  MAILING ADDRESS
---------------------------------------------  ---------------------------------------------
         Mark P. Tanoury                       Cooley Godward LLP
                                               3000 Sand Hill Road, Building 3, Suite 230
                                               Menlo Park, CA 94025
</TABLE>
 
    IN WITNESS WHEREOF, this Certificate has been subscribed this 1st day of
June, 1998 by the undersigned who affirms that the statements made herein are
true and correct.
 
                                          /s/ Mark P. Tanoury
                                          --------------------------------
                                           Mark P. Tanoury
 
                                          SOLE INCORPORATOR
 
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