<PAGE>
 
                                                                     EXHIBIT 3.1

                                                                                

                           CERTIFICATE OF AMENDMENT

                                      OF

                         CERTIFICATE OF INCORPORATION

     Advanstar Holdings, Inc., a corporation organized and existing under and by
virtue of the General Corporation Law of the State of Delaware, DOES HEREBY
CERTIFY:

     FIRST:    That the Board of Directors of Advanstar Holdings, Inc. (the
"Corporation"), by a unanimous written consent effective as of March 17, 1999,
duly and validly adopted the following resolutions:


RESOLVED:  That, subject to stockholder approval, the Corporation amend its
           Certificate of Incorporation as filed with the Secretary of State of
           the State of Delaware (the "Certificate of Incorporation") so that,
           as amended and restated, Article FIRST of the Certificate of
           Incorporation shall be read in its entirety as set forth on 
           Exhibit A attached hereto.
           ---------

RESOLVED:  That the foregoing amendment is hereby recommended to the
           stockholders of the Corporation as being advisable and in the best
           interests of the Corporation and its stockholders.

RESOLVED:  That the proposal to amend the Certificate of Incorporation, as set
           forth in the preceding resolution, be submitted to the stockholders
           of the Corporation for their approval in compliance with Section 
           242 and 228 of the General Corporation Law of the State of Delaware.

RESOLVED:  That, subject to approval by the stockholders of the proposal to
           amend the Certificate of Incorporation as described in the foregoing
           resolution, the Chief Executive Officer or Chief Financial Officer
           be, and each of them acting singly hereby is, authorized and directed
           to amend the Certificate of Incorporation as set forth above and to
           file such amendment with the Secretary of State of the State of
           Delaware.

     SECOND:  That the sole stockholder of the corporation has duly adopted
such resolutions by a written consent effective as of March 17, 1999, in
accordance with the provisions of Section 228 of the General Corporation Law of
the State of Delaware.

     THIRD:  That the aforesaid amendment was duly adopted in accordance with
the applicable provisions of Section 242 of the General Corporation Law of the
State of Delaware.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
<PAGE>
 
     IN WITNESS WHEREOF, said Advanstar Holdings, Inc. has caused this
certificate to be executed by David W. Montgomery, its Chief Financial Officer,
on this 17th day of March, 1999.

                              ADVANSTAR HOLDINGS, INC.


                              By:  /s/ David W. Montgomery
                                   -----------------------
                                   David W. Montgomery
                                   Chief Financial Officer
<PAGE>
 
                                                                       Exhibit A
                                                                       ---------


     FIRST.  The name of the corporation is Advanstar, Inc.
<PAGE>
 
                  CERTIFICATE OF OWNERSHIP AND MERGER MERGING
           ADVANSTAR HOLDINGS, INC. WITH AND INTO AHI HOLDING CORP.


     The undersigned, being a duly authorized officer of AHI HOLDING CORP., a
Delaware corporation (the "Corporation") does hereby certify, pursuant to
Section 253 of the General Corporation Law of the State of Delaware, to the
following information relating to the merger of ADVANSTAR HOLDINGS, INC., a
Delaware corporation ("Advanstar Holdings"), with and into the Corporation:

1. The Corporation was incorporated on April 11, 1996 pursuant to and in
   accordance with the General Corporation Law of the State of Delaware.

2. The Corporation owns 100% of the outstanding shares of capital stock, $.01
   par value per share, of Advanstar Holdings, a corporation incorporated on
   November 19, 1993 pursuant to and in accordance with the General Corporation
   Law of the State of Delaware.

3. The Board of Directors of the Corporation unanimously consented on April 7,
   1998 to the adoption of the following resolutions, which resolutions provided
   that Advanstar Holdings be merged with and into the Corporation:

RESOLVED:  That, the Corporation merge (the "Merger") into itself Advanstar
           Holdings, Inc., its wholly-owned subsidiary and a Delaware
           Corporation ("Holdings"); that the Agreement and Plan of Merger by
           and between the Corporation and Holdings, in substantially the form
           attached hereto as Exhibit A (the "Agreement and Plan of Merger"),

           be, and it hereby is, adopted and approved; that; as provided in the
           Agreement and Plan of Merger, the Certificate of Incorporation be
           amended as of the effective time of the Merger so as to change the
           name of the Corporation to Advanstar Holdings, Inc.; and that the
           Chairman and Chief Executive Officer of the Corporation is hereby
           authorized, acting singly, to execute and deliver the Agreement and
           Plan of Merger in the name and on behalf of the Corporation, with
           such additions, deletions or changes therein as the Chairman and
           Chief Executive Officer may, acting alone, in his sole discretion,
           deem necessary, desirable, convenient or appropriate and consistent
           with the best interests of the Corporation, his execution and
           delivery thereof to be conclusive evidence of his authority to so act
           and of this approval thereof.

RESOLVED:  That, the officers of the Corporation are hereby directed to make,
           execute and acknowledge a Certificate of Ownership and Merger and to
           cause the same to be filed in the office of the Secretary of State of
           Delaware and to do all acts and things whatsoever, whether within or
           without the State of Delaware, which may be necessary or proper to
           effect the Merger and the foregoing resolution; and that the Merger
           shall become effective upon the effective filing of all documents or
<PAGE>
 
           instruments necessary to perfect the Merger pursuant to the
           requirements of the General Corporation Law of the State of Delaware
           and the laws of the State of Delaware.

RESOLVED:  That the officers of the Corporation be, and each of the officers
           acting alone hereby is, authorized and empowered, for and on behalf
           of the Corporation, to execute and deliver any and all other
           documents, papers or instruments and to do or cause to be done any
           and all such acts and things as they, or any of them, may deem
           necessary, appropriate or desirable in order to enable the
           Corporation fully and promptly to carry out the purposes and intents
           of the foregoing resolutions.

                  [Remainder of Page Intentionally Left Blank]
<PAGE>
 
     IN WITNESS WHEREOF, the undersigned has caused this Certificate of
Ownership and Merger to be duly executed and delivered on behalf of the
Corporation this 10th day of June, 1998.

                              AHI HOLDING CORP.


                              By:  /s/ Robert L. Krakoff
                                   ---------------------
                                   Robert L. Krakoff
                                   Chairman and Chief Executive Officer



ATTEST:


/s/ David W. Montgomery
-----------------------
David W. Montgomery
Secretary
<PAGE>
 
                                   Exhibit A

                         AGREEMENT AND PLAN OF MERGER


          AGREEMENT AND PLAN OF MERGER (the "Agreement") dated as of the 10th
day of June, 1998 by and between AHI Holding Corp., a corporation organized
under the laws of the State of Delaware ("AHI"), and Advanstar Holdings, Inc., a
corporation organized under the laws of the State of Delaware and a wholly-owned
subsidiary of AHI ("Holdings"). The two corporations are hereinafter sometimes
called the "Constituent Corporations." Holdings is hereinafter also sometimes
referred to as the "Merged Corporation," and AHI is hereinafter also sometimes
referred to as the "Surviving Corporation."

          WITNESSETH THAT:

          WHEREAS, the Constituent Corporations deem it advisable and generally
to the welfare of the Constituent Corporations that Holdings be merged with and
into AHI under the terms and conditions hereinafter set forth, such merger to be
effected pursuant to the statutes of the State of Delaware; and

          WHEREAS, AHI by its Certificate of Incorporation has an authorized
capital stock consisting of 20,000,000 shares of Common Stock, $.01 par value
per share, of which 16,733,333 shares of such Common Stock are now issued and
outstanding; and

          WHEREAS, Holdings by its Certificate of Incorporation has an
authorized capital stock consisting of 3,000,000 shares of Common Stock, no par
value, of which 100 shares are now issued and outstanding, all of which are
owned solely by AHI, and 100,000 shares of Preferred Stock, $.01 par value per
share, of which no shares are outstanding; and

          NOW, THEREFORE, the Constituent Corporations, parties to this
Agreement, in consideration of the mutual covenants, agreements and provisions
hereinafter contained, do hereby prescribe the terms and conditions of such
merger and mode of carrying the same into effect as follows:

          FIRST:  AHI hereby merges into itself Holdings and Holdings shall be
and hereby is merged into AHI, which shall be the Surviving Corporation.  The
separate existence of Holdings shall cease at the effective time of the merger,
except insofar as it may be continued by law or in order to carry out the
purposes of this Agreement and except as continued in the Surviving Corporation.

          SECOND:  The Certificate of Incorporation of AHI, as in effect at the
time of the merger provided for in this Agreement, shall continue in full force
and effect as the Certificate of Incorporation of the Surviving Corporation
until the same shall be altered, amended or repealed as provided therein or in
accordance with the law; provided that the Certificate of the AHI shall
<PAGE>
 
be amended at the effective time of the merger to provide the name of the
Surviving Corporation shall be Advanstar Holdings, Inc.

          THIRD:  The effect of the Merger on the outstanding shares of the
capital stock of the Merged Corporation shall be as follows:

          (a) Each share of Common Stock of the Merged Corporation which shall
be outstanding at the effective time of the merger, and all rights in respect
thereof shall, without any further action on the part of anyone, be canceled.

          (b) After the effective time of the merger, each holder of a
certificate or certificates which theretofore represented shares of Common Stock
of the Merged Corporation shall cease to have any rights as a stockholder of the
Merged Corporation except as such are expressly reserved to such stockholder by
statute.

          FOURTH: The terms and conditions of the merger are as follows :

          (a) The by-laws of AHI as they shall exist at the effective time of
the merger shall be and remain the by-laws of the Surviving Corporation until
the same shall be altered, amended and repealed as therein provided or in
accordance with law.

          (b) The directors and officers of AHI shall continue in office until
the next annual meeting of stockholders or directors, respectively, and until
their successors shall have been elected and qualified.

          (c) At and after the effective time of the merger, the Surviving
Corporation shall succeed to and possess, without further act or deed, all the
rights, privileges, obligations, powers and franchises, both public and private,
and all of the property, real, personal and mixed, of each of the Constituent
Corporations; all debts due to either of the Constituent Corporations on
whatever account, as well as for stock subscriptions, shall be vested in the
Surviving Corporation; all claims, demands, property, rights, privileges, powers
and franchises and every other interest of either of the Constituent
Corporations shall be as effectively the property of the Surviving Corporation
as they were of the respective Constituent Corporations; the title to any real
estate vested by deed or otherwise in either of the Constituent Corporations
shall not revert or be in any way impaired by reason of the merger, but shall be
vested in the Surviving Corporation; all rights of creditors and all liens upon
any property of either of the Constituent Corporations shall be preserved
unimpaired; all debts, liabilities and duties of the respective Constituent
Corporations shall thenceforth attach to the Surviving Corporation and may be
enforced against it to the same extent as if such debts, liabilities and duties
had been incurred or contracted by it; and the Surviving Corporation shall
indemnify and hold harmless the officers and directors of each of the
Constituent Corporations against all such debts, liabilities and duties and
against all claims and demands arising out of the merger.

          (d) As and when requested by the Surviving Corporation or by its
successors or assigns, the Merged Corporation will execute and deliver or cause
to be executed and delivered all such 
<PAGE>
 
deeds and instruments and will take or cause to be taken all such further action
that the Surviving Corporation may deem necessary or desirable in order to vest
in and confirm to the Surviving Corporation title to and possession of any
property of either of the Constituent Corporations acquired by the Surviving
Corporation by reason or as a result of the merger herein provided for and
otherwise to carry out the intent and purposes hereof, and the officers and
directors of the Merged Corporation and the officers and directors of the
Surviving Corporation are fully authorized in the name of the Merged Corporation
or otherwise to take any and all such action.

          (e) This Agreement shall not be submitted to the stockholders of each
of the Constituent Corporations as permitted by law and specifically by Section
253 of the General Corporation Law of the State of Delaware (the "DGCL").  The
merger shall take effect when any and all documents or instruments necessary to
perfect the merger, pursuant to the requirements of the DGCL, are accepted for
filing by the Secretary of State of the State of Delaware.

          (f) This Agreement may be terminated or abandoned by the mutual
consent of the Constituent Corporations, each acting by its Board of Directors
prior to the effective time of the merger.  In the event of such termination or
abandonment, this Agreement shall become wholly void and of no effect and there
shall be no further liability or obligation hereunder on the part of either of
the Constituent Corporations or of its Board of Directors or stockholders.

          (g) All corporate acts, plans, policies, approvals and authorizations
of Holdings, its stockholders, Board of Directors, committees elected or
appointed by the Board of Directors, officers and agents, which were valid and
effective immediately prior to the effective time of the merger, shall be taken
for all purposes as the acts, plans, policies, approvals and authorizations of
the Surviving Corporation and shall be effective and binding thereon as they
were on Holdings.  The employees of Holdings shall become the employees of the
Surviving Corporation and continue to be entitled to the same rights and
benefits they enjoyed as employees of Holdings.

          (h) From the effective time of the merger, the officers and directors
of the Surviving Corporation are hereby authorized in the name of the
corporations that were the Constituent Corporations to execute, acknowledge and
deliver all instruments and do all things as may be necessary or desirable to
vest in the Surviving Corporation any property or rights of either of the
Constituent Corporations or to carry out the purposes of this Agreement.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
<PAGE>
 
          IN WITNESS WHEREOF, the parties to this Agreement, pursuant to the
approval and authority duly given by resolutions adopted by their respective
Boards of Directors, have caused these presents to be executed by the Chairman
and Chief Executive Officer and attested by the Secretary, as indicated below,
of each party hereto.

                              AHI HOLDING CORP.


                              By:  /s/ Robert L. Krakoff
                                   ---------------------
                                   Robert L. Krakoff
                                   Chairman and Chief Executive Officer


ATTEST:


/s/ David W. Montgomery
-----------------------
David W. Montgomery
Secretary


                              ADVANSTAR HOLDINGS, INC.


                              By:  /s/ Robert L. Krakoff
                                   ---------------------
                                   Robert L. Krakoff
                                   Chairman and Chief Executive Officer


ATTEST:


/s/ David W. Montgomery
-----------------------
David W. Montgomery
Secretary
<PAGE>
 
                   CERTIFICATE OF AMENDMENT OF CERTIFICATE OF
                      INCORPORATION OF AHI HOLDING CORP.

          AHI Holding Corp., a corporation organized and existing under and by
virtue of the General Corporation Law of the State of Delaware, DOES HEREBY
CERTIFY:

          FIRST: Article Fourth of the Certificate of Incorporation of this
corporation be amended to read as follows:

          FOURTH:  This corporation is authorized to issue only one class
of shares of stock and the total number of shares which this corporation is
authorized to issue is 20,000 with a par value of $0.01 per share. Upon the
amendment of this article to read as herein set forth, each outstanding share is
split up and converted into 100 shares.

          SECOND:  That said amendment to the Certificate of Incorporation
herein certified has been duly adopted in accordance with the provisions of
Section 242 of the General Corporation Law of the State of Delaware and has been
consented to in writing by the stockholders, and written notice has been given,
in accordance with Section 228 of the General Corporation Law of the State of
Delaware.

          IN WITNESS WHEREOF, said corporation has caused this Certificate to be
signed by Mitchell Cohen, its authorized officer, this 20th day of May, 1997.
          --------------                                                     

                                   By: /s/ Mitchell Cohen
                                       -------------------
                                       Mitchell Cohen
                                       Title:  Vice President
<PAGE>
 
           CERTIFICATE OF CORRECTION OF AMENDMENT OF CERTIFICATE OF
                      INCORPORATION OF AHI HOLDING CORP.

          AHI Holding Corp., a corporation organized and existing under and by
virtue of the General Corporation Law of the State of Delaware, pursuant to
Section 103 (f) of the General Corporation Law of the State of Delaware:

          FIRST:  The Certificate of Amendment of the Certificate of
Incorporation of AHI Holding Corporation dated May 28, 1996 (the "Amendment")
inaccurately states such Amendment, in that such certificate purported to change
the par value of the corporation's common stock from $0.01 per share to shares
without par value.

          SECOND: Article First of the Certificate of Amendment is corrected as
follows:

          FIRST:  That the Board of Directors of said corporation at a meeting
duly convened and held, adopted the following resolution:

          RESOLVED, that the Board of Directors hereby declares it advisable and
in the best interest of the corporation that Article Fourth of the Certificate
of Incorporation be amended to read as follows:

          FOURTH: The total number of shares of stock which this corporation is
authorized to issue is 200,000 with a par value of $0.01 per share.

          IN WITNESS WHEREOF, said corporation has caused this Certificate to be
signed by the undersigned officers this 30th day of May, 1996.

 

                              By: /s/ Mitchell R. Cohen
                                  ---------------------
                                  Mitchell R. Cohen
                                  Title:  Vice President


ATTEST:

/s/ Paul J. Mundie
------------------
By:  Paul J. Mundie
     Assistant Secretary
<PAGE>
 
        CERTIFICATE OF AMENDMENT OF CERTIFICATE OF INCORPORATION OF AHI
                                 HOLDING CORP.

          AHI Holding Corp., a corporation organized and existing under and by
virtue of the General Corporation Law of the State of Delaware, DOES HEREBY
CERTIFY:

          FIRST: That the Board of Directors of said corporation at a meeting
duly convened and held, adopted the following resolution:

          RESOLVED, that the Board of Directors hereby declares it advisable and
in the best interest of the corporation that Article Fourth of the Certificate
of Incorporation be amended to read as follows:

          FOURTH: The total number of shares of stock which this corporation is
authorized to issue is 200,000 without par value.

          SECOND: That the said amendment has been consented to and authorized
by the holders of a majority of the issued and outstanding stock entitled to
vote by written consent given in accordance with the provisions of Section 228
of the General Corporation Law of the State of Delaware.

          THIRD: That the aforesaid amendment was duly adopted in accordance
with the applicable provisions of Section 242 and 228 of the General Corporation
Law of the State of Delaware.

          IN WITNESS WHEREOF, said corporation has caused this Certificate to be
signed by                this 28th day of May, 1996.
          --------------      ----



                                   /s/ Mitchell R. Cohen
                                   ---------------------
                                   By:  Mitchell R. Cohen,
                                        Vice President


ATTEST:

 
-------------------------
By:  Timothy G. _________
<PAGE>
 
               CERTIFICATE OF INCORPORATION OF AHI HOLDING CORP.

          FIRST.  The name of the corporation is AHI Holding Corp.
          -----

          SECOND.  The address of the corporation's registered office in the
          ------                                                              
State of Delaware is 1013 Centre Road, City of Wilmington, County of New Castle.
Its registered agent at that address is Corporation Service Company.

          THIRD.  The nature of the business or purposes to be conducted or
          -----
promoted by the corporation is to engage in any lawful act or activity of which
corporation may be organized under the General Corporation Law of the State of
Delaware (the "GCL").

          FOURTH.  The total number of shares of all classes of capital stock
          ------                                                               
which the corporation is authorized to issue is 3,000 shares of common stock
with a par value of $0.01 per share.

          FIFTH. The name and mailing address of the corporation's sole
          -----
incorporator is:

                  Bonnie Thompson
                  Heller Ehrman White & McAuliffe
                  333 Bush Street
                  San Francisco, CA   94104

          SIXTH.  The corporation shall have a perpetual existence.
          -----

          SEVENTH.   No director of the corporation shall be personally liable
          -------                                                             
to the corporation or any of its stockholders for monetary damages for 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 GLC or (iv) for any
transaction from which the director derived any improper personal benefit.  If
the GCL is amended to authorize or require corporate action that further
eliminates or limits the personal liability of directors, then the liability of
the directors of the corporation shall be eliminated or limited to the fullest
extent permitted by the GCL, as so amended.  Any repeal or modification of this
Article SEVENTH shall not adversely affect any right or protection of a director
of the corporation existing at the time of the repeal or modification.

          EIGHTH. In addition to all powers granted to the board of directors
          ------
under the GCL:

          A.  The board of directors of the corporation is expressly authorized
to make, alter or repeal the by-laws of the corporation.

          B. Elections of directors need not be by written ballot unless the by-
laws of the corporation shall so provide.
<PAGE>
 
          C.  The books of the corporation may be kept at such place within or
without the State of Delaware as the by-laws of the corporation may provide or
as may be designated from time to time by the board of directors of the
corporation.

          NINTH.  The corporation reserves the right to amend or repeal any
          -----                                                            
provision contained in this Certificate of Incorporation in the manner now or
hereafter prescribed by statute. All rights conferred upon the corporation's
stockholders are granted subject to this reservation.

                              *        *        *

          Being the sole incorporator, for the purpose of forming a corporation
pursuant to the GCL, I do make this certificate, hereby declaring and certifying
that this is my act and deed and the facts stated above are true, and
accordingly have hereunto set my hand on April 11, 1996.

                                   /s/ Bonnie Thompson
                                   -------------------
                                   Bonnie Thompson,
                                   Sole Incorporator