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                                                                       EXHIBIT 5


                                        February 4, 1999


Cardinal Health, Inc.
5555 Glendon Court
Dublin, OH  43016

Gentlemen:

                  I have acted as counsel to Cardinal Health, Inc., an Ohio
corporation (the "Company"), in connection with Company's Registration
Statement on Form S-8 (the "Registration Statement") filed under the Securities
Act of 1933, as amended (the "Act") relating to the issuance of up to
3,000,000 common shares, without par value (the "Common Shares"), of the
Company pursuant to the Allegiance Retirement Plan (the "Plan").

                  In connection with the foregoing, I have examined: (a) the
Amended and Restated Articles of Incorporation, as amended, and Restated Code of
Regulations, as amended, of the Company, (b) the Plan, and (c) such records of
the corporate proceedings of the Company and such other documents as I deemed
necessary to render this opinion.

                  Based on such examination, I am of the opinion that the Common
Shares available for issuance under the Plan, when issued, delivered and paid
for in accordance with the terms and conditions of the Plan, will be legally
issued, fully paid and nonassessable.

                  I hereby consent to the filing of this Opinion as Exhibit 5 to
the Registration Statement and the reference to me in Item 5 of Part II of the
Registration Statement. In giving such consent, I do not thereby admit that I am
in the category of person whose consent is required under Section 7 of the Act
or the rules and regulations of the Securities and Exchange Commission.

                                        Very truly yours,
                                        
                                        /s/ Paul S. Williams
                                        Paul S. Williams, Esq.
                                        Assistant General Counsel