EXHIBIT 4.5

                                A.M. CASTLE & CO.


                           FIRST AMENDMENT AND WAIVER
                                TO NOTE AGREEMENT

                                   $25,000,000
                               7.54% Senior Notes
                                Due May 30, 2009


                                                    Dated as of December 1, 1998


Massachusetts Mutual Life
Insurance Company
1295 State Street
Springfield, MA 01111

United of Omaha Life
Insurance Company
Mutual of Omaha Plaza
Omaha, NE 68175

Ladies and Gentlemen:

     Reference is made to the Note Agreement dated as of May 15, 1997 (the "Note
Agreement") among A.M. Castle & Co. (the "Company"), Massachusetts Mutual Life
Insurance Company and United of Omaha Life Insurance Company, pursuant to which
the Company issued $25,000,000 principal amount of its 7.54% Senior Notes (the
"Notes"). You are referred to herein individually as a "Holder" and collectively
as the "Holders." Schedule I hereto indicates the original principal amount of
Notes held by each of you. Capitalized terms used and not otherwise defined
herein shall have the meanings ascribed to them in the Note Agreement.

     The Company was in breach of the Net Working Capital Covenant contained in
Section 7.3 of the Note Agreement as of September 30, 1998. Consequently, the
Company has requested the waiver and modification of that covenant of the Note
Agreement. The Holders are willing to grant an amendment and waiver on the terms
and conditions hereinafter set forth.

     In consideration of the premises and for good and valuable consideration,
the receipt and sufficiency of which are acknowledged, the Company and the
Holders agree as follows:

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     SECTION 1. AMENDMENTS

     1.1. Amendment of Section 7.3. Section 7.3 of the Note Agreement is amended
to read in its entirety as fo11ows:

          "7.3. Net Working Capital. The Company will not permit the ratio
     (calculated on the last day of each fiscal quarter) of Net Working Capital
     to Consolidated Debt to be less than 1.0 to 1.0."

     SECTION 2. WAIVER AND CONSENT

     2.1. Waiver. The Holder waives compliance by the Company with the
provisions of Section 7.3 of the Note Agreement for the quarter ending September
30, 1998.

     2.2 Limitation on Waiver. The waiver under Section 2.1 hereof is limited
precisely to its terms and shall not constitute a waiver generally or in any
other instance. Nothing contained herein shall be deemed a waiver of (or
otherwise affect the Holders' ability to enforce) any Default or Event of
Default other than as expressly set forth herein.

     SECTION 3. REAFFIRMATION; REPRESENTATIONS AND WARRANTIES

     3.1. Reaffirmation of Note Agreement. The Company reaffirms its agreement
to comply with each of the covenants, agreements and other provisions of the
Note Agreement and the Notes, including the additions and amendments of such
provisions effected by this First Amendment and Waiver.

     3.2. Note Agreement The Company represents and warrants that, subject to
the effectiveness of this First Amendment and Waiver, the representations and
warranties contained in the Note Agreement are true and correct as of the date
hereof, except for such changes, facts, transactions and occurrences that have
arisen since May 15, 1997 in the ordinary course of business and such other
matters as have been previously disclosed in writing by the Company to the
Holders.

     3.3. No Default or Event of Default. After giving effect to the
transactions contemplated hereby, no Default or Event of Default will exist.

     3.4. Authorization. The execution, delivery and performance by the Company
of this First Amendment and Waiver have been duly authorized by all necessary
corporate and other action and do not and will not require any registration
with, consent or approval of; notice to or action by, any Person (including any
Governmental Authority) in order to be effective and enforceab1e. Each of the
Note Agreement and this First Amendment and Waiver constitutes the legal, valid
and binding obligations of the Company, enforceable against it in accordance
with its respective terms, without defense, counterclaim or offset.

     SECTION 4. EFFECTIVE DATE

     This First Amendment and Waiver shall become effective upon: (i) execution
by Holders of at least 51% of an aggregate principal amount of the Notes
outstanding of counterparts of this First Amendment and Waiver and (ii) receipt
by each Holder of payment of the amendment fee required by Section 5(a) hereof.

                                        2
<PAGE>


     SECTION 5. AMENDMENT FEE; EXPENSES

     (a) Amendment Fee. As consideration for the approval by the Holders of this
First Amendment and Waiver, the Company will pay to each Holder, whether or not
such Holder executes this First Amendment and Waiver, an amendment fee equal to
0.15% of the principal amount of the outstanding Notes held by such Holder. Such
fee shall be paid in accordance with the instructions set forth in the Note
Agreement.

     (b) Expenses. The Company shall pay (within two business days of receipt of
a detailed statement therefor) all reasonab1e fees and expenses of special
counsel to the Holders.

     SECTION 6. MISCELLANEOUS

     6.1. Ratification. Except to the extent amended, modified, deleted or added
to hereby, the terms and provisions of the Note Agreement, including the
representations and warranties contained therein, shall remain in full force and
effect and are ratified, confirmed, remade and approved in all respects as of
the date hereof.

     6.2. Reference to and Effect on the Note Agreement. Upon the final
effectiveness of this First Amendment and Waiver, each reference in the Note
Agreement and in other documents describing or referencing the Note Agreement to
the "Agreement," "Note Agreement," "hereunder," "hereof," "herein," or words of
like import referring to the Note Agreement, shall mean and be a reference to
the Note Agreement, as amended hereby.

     6.3. Binding Effect. This First Amendment and Waiver shall be binding upon
and inure to the benefit of the respective successors and assigns of the parties
hereto.

     6.4. Governing Law. This First Amendment and Waiver shall be governed by
and construed in accordance with Illinois law.

     6.5. Counterparts. This First Amendment and Waiver may be executed in any
number of counterparts, each executed counterpart constituting an original, but
altogether only one instrument.

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<PAGE>


    IN WITNESS WHEREOF, the Company and the Holders have caused this First
Amendment and Waiver to be executed and delivered by their respective officer
or  officers thereunto duly authorized.


                                        A.M. CASTLE & CO.


                                        By: /s/ James A. Podojil
                                        Name: James A. Podojil
                                        Title: Treasurer


                                        MASSACHUSETTS MUTUAL LIFE
                                           INSURANCE COMPANY


                                        By: /s/ Lawrence Stillman
                                        Name: Lawrence Stillman
                                        Title: Managing Director


                                        UNITED OF OMAHA LIFE INSURANCE
                                           COMPANY


                                        By: /s/ Curtis R. Caldwell
                                        Name: Curtis R. Caldwell
                                        Title: First Vice President



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<PAGE>


                                   SCHEDULE I



                                                          Original
Name of Purchaser                                     Principal Amount
-----------------                                     ----------------

Massachusetts Mutual Life Insurance Company             $18,000,000
United of Omaha Life Insurance Company                    7,000,000