EXHIBIT 5.1


                                          June 18, 1998


Advanstar Communications Inc.
7500 Old Oak Boulevard
Cleveland, Ohio 44130-3369


Dear Ladies and Gentlemen:

         We are counsel to Advanstar Communications Inc., a New York corporation
(the "Company") in connection with the registration on a Registration Statement
on Form S-4 (the "Registration Statement") and the prospectus forming a part
thereof (the "Prospectus") under the Securities Act of 1933, as amended, of
$150,000,000 aggregate principal amount of the Company's 9-1/4% Senior
Subordinated Notes due 2008 (the "Exchange Notes") and the related guarantees
(the "Guarantees") of certain of the Company's subsidiaries named in the
Registration Statement (the "Guarantors"). The Exchange Notes and the Guarantees
are proposed to be issued under an indenture dated as of April 30, 1998 (the
"Indenture") between the Company and the Bank of New York, as trustee, and the
related Exchange and Registration Rights Agreement (the "Registration Rights
Agreement"), dated April 30, 1998, among the Company, the Guarantors and the
Initial Purchasers (as defined in the Registration Rights Agreement) in exchange
for the Company's 9-1/4% Senior Subordinated Notes Due 2008 and related
guarantees (the "Original Notes").

         We have examined such documents, records and matters of law as we have
deemed necessary for purposes of this opinion. We have assumed that the Exchange
Notes and the Guarantees will be executed and delivered as set forth in the
Registration Statement, the Prospectus and the Letter of Transmittal set forth
as an exhibit to the Registration Statement. We have assumed the genuineness of
all signatures and the conformity to original documents of all copies of
documents submitted to us as copies, whether certified or not. We have assumed
the conformity of the certificates for the Exchange Notes and the Guarantees to
the specimens of the certificates, which are included as an exhibit to the
Registration Statement. We have assumed that the Exchange Notes, the Guarantees
and the Indenture have been duly authorized, executed and authenticated in
accordance with the terms of the Indenture by each of the parties thereto. Our
opinion expressed herein with respect to the validly and binding effect of the
Exchange Notes and the Guarantees is qualified to the extent that the validity
and binding effect thereof may be limited by (i) applicable bankruptcy,
reorganization, arrangements, insolvency, moratorium or similar laws affecting
the enforcement of creditors' rights generally as at the time in effect and (ii)
general principles of equity (whether considered in a proceeding of law or in
equity).

         We are members only of the bar of the Commonwealth of Massachusetts and
therefore do not hold ourselves out as experts in, and express no opinion as to,
the laws of any other state or 

 
Advanstar Communications Inc.
June 18, 1998
Page 2

jurisdiction other than the laws of the Commonwealth of Massachusetts and the
federal laws of the United States of America. The Indenture and the Exchange
Notes provide that each is governed by the laws of the State of New York,
without giving effect to the conflict of laws provisions thereof. We have
assumed for purposes of this opinion that the substantive laws of the State of
New York are the same as the substantive laws of the Commonwealth of
Massachusetts. We have also assumed that the choice of law provisions of the
Indenture and the Exchange Notes would be given effect.

         Based upon and subject to the foregoing, we are of the opinion that the
Exchange Notes and the Guarantees, when duly executed and authenticated in
accordance with the terms of the Indenture and delivered in exchange for the
Original Notes as contemplated in the Prospectus, will be valid and binding
obligations of the Company.

         We consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to us under the caption "Legal
Matters" in the Registration Statement.

                                            Very truly yours,
  
                                            /s/ Testa, Hurwitz & Thibeault, LLP
  
                                            TESTA, HURWITZ & THIBEAULT, LLP