<PAGE>

                                                                    EXHIBIT 10.5

                  FIRST AMENDMENT TO CREDIT AGREEMENT

                  FIRST AMENDMENT (this "First Amendment"), dated as of January
17, 2003, to the Amended and Restated Credit Agreement, dated as of March 8,
2002 (as heretofore amended, the "Credit Agreement"), among PENTON MEDIA, INC.
(the "Borrower"), the Lenders party thereto, BANK OF AMERICA, N.A., as
Syndication Agent, BANK ONE, NA and FLEET NATIONAL BANK, as Co-Documentation
Agents, and THE BANK OF NEW YORK, as Administrative Agent.

                              W I T N E S S E T H:

                  WHEREAS, the Borrower, the Lenders, the Syndication Agent, the
Co-Documentation Agents and the Administrative Agent are parties to the Credit
Agreement;

                  WHEREAS, the Borrower has requested that the Lenders, the
Syndication Agent, the Co-Documentation Agents and the Administrative Agent
amend the Credit Agreement as set forth herein; and

                  WHEREAS, the Lenders, the Syndication Agent, the
Co-Documentation Agents and the Administrative Agent are willing to agree to
such amendment to the Credit Agreement, subject to the terms and conditions set
forth herein.

                  NOW, THEREFORE, in consideration of the premises and mutual
covenants contained herein, the Borrower, the Lenders, the Syndication Agent,
the Co-Documentation Agents and the Administrative Agent hereby agree as
follows:

                  1.       Defined Terms. Unless otherwise defined herein,
capitalized terms used herein shall have the meanings set forth in the Credit
Agreement.

                  2.       Amendment to Section 1.1 (Defined Terms). Section 1.1
of the Credit Agreement is hereby amended by deleting in its entirety the
definition of "Commitment Fee Margin" and inserting in lieu thereof the
following definition:

                  "Commitment Fee Margin" means 0.75%.

                  3.       Amendment to Section 1.1 (Defined Terms). Section 1.1
of the Credit Agreement is hereby further amended by (i) deleting the "." at the
end of the definition of "Eligible Receivables" and inserting in lieu thereof ";
or"; and (ii) inserting the following new clause (p) at the end of the
definition of "Eligible Receivables" thereby providing that, along with the
others listed, a Receivable shall not be included in calculating Eligible
Receivables if:

                  "(p) such Receivable arises from a trade show that has been
completed."

                  4.       Amendment to Section 1.1 (Defined Terms). Section 1.1
of the Credit Agreement is hereby further amended by adding the following
definitions of

<PAGE>

"Aggregate Gross Proceeds," "Asset Disposition," "First Amendment Effective
Date" and "Pending Asset Disposition" each in appropriate alphabetical order:

                  "Aggregate Gross Proceeds" has the meaning assigned to such
                  term in Section 2.5(c).

                  "Asset Disposition" has the meaning assigned to such term in
                  Section 2.5(c).

                  "First Amendment Effective Date" means the date on which the
                  First Amendment to the Credit Agreement becomes effective in
                  accordance with the terms of such First Amendment.

                  "Pending Asset Disposition" means (and is limited to) the
                  disposition of the assets and/or Equity Interests of one or
                  more of the following of the Borrowers' operations: (i)
                  Professional Trade Shows/ISOA; and/or (ii) Used Equipment
                  Directory.

                  5.       Amendment to Section 1.1 (Defined Terms). Section 1.1
of the Credit Agreement is hereby further amended by deleting the second and
third sentences of the definition of "Revolving Commitment" and inserting in
lieu thereof the following:

                  "The amount of each applicable Lender's Revolving Commitment
                  is set forth on Schedule 2.1, or in the Assignment and
                  Acceptance pursuant to which such Lender shall have assumed
                  its Revolving Commitment, as applicable. The total Revolving
                  Commitments shall be $32,000,000."

                  6.       Amendment to Section 2.5 (Termination and Reduction
of Revolving Commitments). Section 2.5 of the Credit Agreement is hereby amended
by (i) re-lettering clauses (c) and (d) thereof as clauses (e) and (f)
respectively; and (ii) inserting the following new clauses (c) and (d):

                  "(c) Immediately upon the closing of one or more sales,
                  transfers, leases or other dispositions of assets and/or
                  dispositions or issuances of Equity Interests (other than
                  Disqualified Equity) by the Borrower and/or any Subsidiaries
                  pursuant to Section 7.5(d) (each an "Asset Disposition"), the
                  Revolving Commitments shall be reduced by fifty percent (50%)
                  times: (i) in the case of a Pending Asset Disposition, (A) the
                  amount of the combined Aggregate Gross Proceeds up to
                  $6,000,000 and (B) the amount by which the combined Aggregate
                  Gross Proceeds exceed $7,500,000; and (ii) in the case of all
                  other Asset Dispositions, the amount of the Aggregate Gross
                  Proceeds. For the purposes of this Section 2.5(c), "Aggregate
                  Gross Proceeds" shall mean all consideration of whatever kind
                  or nature received or to be received by the Borrower and/or
                  any Subsidiary in connection with an Asset Disposition,
                  including but not limited to the maximum amount of

                                       2

<PAGE>

                  any and all contingent and/or unliquidated payments that may
                  be received at any time by the Borrower."

                  "(d) There shall be an automatic one-time reduction in the
                  Revolving Commitments of $10,000,000, in addition to any other
                  reductions provided for in this Credit Agreement (including
                  but not limited to those in Section 2.5 (b) and (c) above), at
                  such time as the aggregate sum of the cash and cash
                  equivalents of the Loan Parties equals or exceeds
                  $40,000,000."

                  7.       Amendment to Section 2.7 (Prepayment of Loans).
Section 2.7 of the Credit Agreement is hereby amended by deleting the fourth
through seventh sentences of clause (e) and inserting in lieu thereof the
following:

                  "Each voluntary partial prepayment of any Borrowing hereunder
                  (other than Swingline Borrowings) shall, when added to the
                  amount of each concurrent prepayment of other Borrowings
                  (other than Swingline Borrowings), be in an integral multiple
                  of $250,000 and not less than $1,000,000."

                  8.       Amendment to Section 6.1 (Financial Statements and
Other Information). Section 6.1 of the Credit Agreement is hereby amended by
deleting clause (d) in its entirety and inserting in lieu thereof the following
new clause (d):

                  "(d) as promptly as practicable, but in any event not later
                  than the 30th day after the end of each calendar month, (1)
                  its consolidated profit and loss statement; and (2) divisional
                  revenue and EBITDA report."

                  9.       Amendment to Section 6.1 (Financial Statements and
Other Information). Section 6.1 of the Credit Agreement is hereby further
amended by deleting clause (g) in its entirety and inserting in lieu thereof the
following new clause (g):

                  "(g) by no later than February 15 of each fiscal year, a
                  budget and business plan for the current fiscal year in the
                  form approved by the Borrower's board of directors, together
                  with a business forecast for the current fiscal year, all in
                  form, scope and detail satisfactory to the Administrative
                  Agent and on a quarterly basis for each fiscal quarter of such
                  succeeding fiscal year;"

                  10.      Amendment to Section 6.1 (Financial Statements and
Other Information). Section 6.1 of the Credit Agreement is hereby further
amended by deleting clause (j) in its entirety and inserting in lieu thereof the
following new clause (j):

                  "(j) as promptly as practicable, but in any event not later
                  than the 15th day after the end of each calendar month, (i) a
                  Borrowing Base Certificate setting forth the Borrowing Base as
                  of last

                                       3

<PAGE>

                  Business Day of such calendar month, together with a detailed
                  aging report with respect to the Receivables and (ii) the cash
                  balance report as of the last day of such calendar month."

                  11.      Amendment to Section 7.5 (Asset Sales; Issuance of
Equity Interests by Subsidiaries). Section 7.5 of the Credit Agreement is hereby
amended by deleting clause (d) in its entirety and inserting in lieu thereof the
following new clause (d):

                  "(d) other sales, transfers, leases and other dispositions of
                  assets by the Borrower or any of its Subsidiaries, and
                  issuances of Equity Interests (other than Disqualified Equity)
                  by the Subsidiaries, provided that (i) (A) subsequent to
                  December 31, 2002, the aggregate fair market value of all
                  assets, sold, transferred, leased or otherwise disposed of,
                  and Equity Interests issued, in reliance upon this clause (d)
                  (but not including the Pending Asset Dispositions), shall not
                  at any time exceeds $3,561,400 in the aggregate, (B) all
                  sales, transfers, leases and other dispositions, and all
                  Equity Interests, issued under this clause (d) other than any
                  Pending Asset Disposition shall be made for fair value and at
                  least eighty-five percent (85%) of the Aggregate Gross
                  Proceeds therefor shall be paid in cash, and (C) at the time
                  thereof and immediately after giving effect thereto no Default
                  shall have occurred and be continuing, or (ii) Super-majority
                  Lenders shall have consented thereto."

                  12.      Amendment to Schedule 2.1. Schedule 2.1 of the Credit
Agreement is hereby amended in its entirety in the form of Schedule 2.1 annexed
hereto.

                  13.      Use of Proceeds. The Borrower hereby acknowledges and
agrees that until such time as the obligations under the Credit Agreement and
other Loan Documents are paid in full and there shall no longer be any
obligation to make Loans or advances or issue letters of credit (or guaranties
in respect thereof) thereunder and there shall no longer be any letter of credit
(or guaranty in respect thereof) outstanding thereunder or such letter of credit
(or guaranty in respect thereof) shall have been fully collateralized (in
accordance with the Loan Documents), the proceeds from the sale of any asset
sale authorized pursuant to Section 7.5(d) of the Credit Agreement, as amended
hereby, shall be distributed in a manner that is not inconsistent with Section
3.4 of the Intercreditor Agreement.

                  14.      Representations and Warranties. The Borrower hereby
confirms, reaffirms and restates the representations and warranties set forth in
Article IV of the Credit Agreement. The Borrower represents and warrants that,
after giving effect to this First Amendment, no Default or Event of Default has
occurred and is continuing.

                  15.      Effectiveness. This First Amendment shall become
effective on the date (the "First Amendment Effective Date") on which (i) the
Administrative Agent receives counterparts of this First Amendment duly executed
by the Borrower and the

                                       4

<PAGE>

Super-majority Lenders; (ii) the Administrative Agent has received from the
Borrower for the account of each Lender that has executed and delivered this
First Amendment to the Administrative Agent by 12:00 noon (New York time) on the
date hereof, an amendment fee equal to 0.125% of the amount of such Lender's
reduced Revolving Commitment (as reflected in the amended Schedule 2.1 annexed
hereto); and (iii) Borrower has paid all fees and expenses of the Administrative
Agent, including but limited to the fees and expenses of its counsel in
connection with the Credit Agreement.

         16.      Continuing Effect of the Credit Agreement. This First
Amendment shall not constitute an amendment, modification or waiver of or in any
way affect any provision of the Credit Agreement or the Loan Documents, except
as expressly provided herein, shall not be construed as a waiver or consent to
any further or future action on the part of the Borrower that would require a
waiver or consent of the Lenders, the Syndication Agent, the Co-Documentation
Agents and the Administrative Agent and shall not by implication or otherwise
limit, impair, constitute a waiver of, or otherwise affect any right, power or
remedy of any Lender, the Syndication Agent, each Co-Documentation Agent or the
Administrative Agent under any of the Loan Documents. Except as expressly
amended hereby, the provisions of the Credit Agreement and the Loan Documents
are and shall remain in full force and effect.

         17.      Counterparts. This First Amendment may be executed by the
parties hereto in any number of separate counterparts (including telecopied
counterparts), each of which shall be deemed to be an original, and all of which
taken together shall be deemed to constitute one and the same instrument.

         18.      GOVERNING LAW. THIS FIRST AMENDMENT AND THE RIGHTS AND
OBLIGATIONS OF THE PARTIES UNDER THIS FIRST AMENDMENT SHALL BE GOVERNED BY, AND
CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

                            [SIGNATURE PAGES FOLLOW]

                                       5

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this First Amendment
to be duly executed by their respective authorized officers as of the day and
year first above written.

                                              PENTON MEDIA, INC.

                                              By: ______________________________
                                              Name: ____________________________
                                              Title: ___________________________

CONSENTED AND AGREED TO:

DONOHUE MEEHAN PUBLISHING COMPANY
INTERNET WORLD MEDIA, INC.
ONE, INC.
PMI TWO, INC.
PENTON INTERNET, INC.
STARDUST.COM
DUKE INVESTMENTS, INC.
DUKE COMMUNICATIONS INTERNATIONAL, INC.
PTS DELAWARE, INC.
TECH CONFERENCES, INCORPORATED
HEALTHWELL.COM, INC.

AS TO EACH OF THE FOLLOWING:

By: _______________________
Name: _____________________
Title: ____________________

<PAGE>

                                             THE BANK OF NEW YORK, individually
                                             and as Administrative Agent

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             BANK OF AMERICA, N.A., individually
                                             and as Syndication Agent

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             BANK ONE, NA, individually and as
                                             a Co-Documentation Agent

                                             By: _____________________________
                                             Name: ___________________________
                                             Title: __________________________

<PAGE>

                                             FLEET NATIONAL BANK, individually
                                             and as a Co-Documentation Agent

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             ALLFIRST BANK

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             BANK OF MONTREAL

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             CREDIT AGRICOLE INDOSUEZ

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             DRESDNER BANK AG, NEW YORK
                                             AND GRAND CAYMAN BRANCHES

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             THE HUNTINGTON NATIONAL BANK

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             PNC BUSINESS CREDIT

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             NATIONAL CITY BANK

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             BNP PARIBAS

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             CITIZENS BANK OF MASSACHUSETTS

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             SUNTRUST BANK

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                                             KEY CORPORATE CAPITAL INC.

                                             By: ______________________________
                                             Name: ____________________________
                                             Title: ___________________________

<PAGE>

                               PENTON SCHEDULE 2.1
                             REVOLVING COMMITMENTS(1)

<TABLE>
<CAPTION>
                LENDER                                  REVOLVING COMMITMENT
--------------------------------------          ----------------------------
<S>                                             <C>
--------------------------------------          ----------------------------
THE BANK OF NEW YORK                                       [$ 4,266,946]
--------------------------------------          ----------------------------
BANK OF AMERICA, N.A.                                      [$  4,419271]
--------------------------------------          ----------------------------
BANK ONE, NA                                               [$ 2,201,758]
--------------------------------------          ----------------------------
FLEET NATIONAL BANK                                        [$ 3,643,608]
--------------------------------------          ----------------------------
ALLFIRST BANK                                              [$ 1,271,860]
--------------------------------------          ----------------------------
BANK OF MONTREAL                                           [$   953,895]
--------------------------------------          ----------------------------
CREDIT AGRICOLE INDOSUEZ                                   [$   953,895]
--------------------------------------          ----------------------------
DRESDNER BANK AG, NEW YORK                                 [$ 2,609,281]
AND GRAND CAYMAN BRANCHES
--------------------------------------          ----------------------------
THE HUNTINGTON NATIONAL BANK                               [$   981,876]
--------------------------------------          ----------------------------
PNC BUSINESS CREDIT                                        [$   815,911]
--------------------------------------          ----------------------------
NATIONAL CITY BANK                                         [$ 2,290,111]
--------------------------------------          ----------------------------
BNP PARIBAS                                                [$ 1,494,435]
--------------------------------------          ----------------------------
CITIZENS BANK OF MASSACHUSETTS                             [$ 2,337,679]
--------------------------------------          ----------------------------
SUNTRUST BANK                                              [$ 1,711,780]
--------------------------------------          ----------------------------
KEY CORPORATE CAPITAL INC.                                 [$ 2,047,694]
--------------------------------------          ----------------------------
TOTAL:                                                      $32,000,000
--------------------------------------          ----------------------------
</TABLE>

-------------------------------

(1)      After giving effect to the reductions upon the First Amendment
Effective Date.