1
                                                                     Exhibit 5.1

                        [Letterhead of Johnson & Johnson]



                                                                  April 23, 2001



Johnson & Johnson
One Johnson & Johnson Plaza
New Brunswick, NJ 08933

Dear Ladies and Gentlemen:

     I am Associate General Counsel of Johnson & Johnson, a New Jersey
corporation (the "Company"), and I am familiar with the Registration Statement
on Form S-4 (the "Registration Statement") being filed by the Company with the
Securities and Exchange Commission under the Securities Act of 1933, as amended,
relating to the proposed issuance of shares of the Company's Common Stock, par
value $1.00 per share ("Common Stock"), in connection with the merger of Express
Merger Sub Inc., a Delaware corporation and a wholly owned subsidiary of the
Company ("Merger Sub"), with and into ALZA Corporation, a Delaware corporation
("ALZA"), pursuant to the terms of the Agreement and Plan of Merger dated as of
March 26, 2001 (the "Merger Agreement"), among the Company, Merger Sub and ALZA.

     I have reviewed the Company's Restated Certificate of Incorporation and
By-laws and such other corporate records of the Company and documents and
certificates of public officials and others as I have deemed necessary as basis
for the opinion hereinafter expressed.

     Based on the foregoing and having regard for such legal considerations as I
deem relevant, I am of the opinion that the shares of Common Stock covered by
the Registration Statement when delivered in exchange for shares of ALZA common
stock pursuant to the Merger Agreement will be duly authorized, validly issued,
fully paid and nonassessable.

     I hereby consent to the use of my name under the caption "Legal Matters" in
the Proxy Statement/Prospectus constituting a part of the Registration Statement
and to the use of this opinion as an Exhibit to the Registration Statement.

                                            Very truly yours,

                                             /s/ Joseph S. Orban
                                             -----------------------------------
                                             Name: Joseph S. Orban
                                             Title: Associate General Counsel