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                      [MORRISON & FOERSTER LLP LETTERHEAD]
 
                                                                     EXHIBIT 8.1
 
                                OCTOBER 28, 1996
 
Nellcor Puritan Bennett Incorporated
4280 Hacienda Drive
Pleasanton, California 94588
 
     Re: Proxy Statement of Aequitron Medical, Inc. and Prospectus of Nellcor
         Puritan Bennett Incorporated
 
Ladies and Gentlemen:
 
     We have acted as counsel to Nellcor Puritan Bennett Incorporated ("NPB") in
connection with the Registration Statement on Form S-4 (the "Registration
Statement") of NPB which includes the Proxy Statement of Aequitron Medical, Inc.
("Aequitron") and Prospectus of NPB (the "Proxy Statement/Prospectus"). Unless
otherwise indicated, any defined terms used herein shall have the meanings
ascribed to them in the Proxy Statement/Prospectus. In rendering this opinion,
we have relied upon letters delivered to Morrison & Foerster LLP by NPB,
Aequitron and affiliates of NPB containing certain representations relevant to
this opinion. We hereby confirm that the discussion under the caption "Certain
Federal Income Tax Consequences" in the Proxy Statement/Prospectus expresses our
opinion as to the material federal income tax consequences to NPB, Aequitron and
the Aequitron shareholders with respect to the Merger, as long as the Merger is
effected in accordance with the terms of an agreement, as amended, dated as of
September 9, 1996, by and between NPB and Aequitron.
 
     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the use of our name under the caption "Certain
Federal Income Tax Consequences" in the Proxy Statement/Prospectus. In providing
this consent, we do not thereby admit that we are in the category of persons
whose consent is required under Section 7 of the Securities Act of 1933, as
amended.
 
                                        Very truly yours,
 
                                        Morrison & Foerster LLP