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                                    EXHIBIT 5.1
                                          
                          [COOLEY GODWARD LLP LETTERHEAD]

December 11, 1998 

Inhale Therapeutic Systems, Inc. 
150 Industrial Road 
San Carlos, CA 94070 

Ladies and Gentlemen: 

You have requested our opinion with respect to certain matters in connection 
with the filing by Inhale Therapeutic Systems, Inc., a Delaware corporation 
(the "Company"), of a Resale Registration Statement on Form S-3 (the 
"Registration Statement") with the Securities and Exchange Commission (the 
"Commission") on December 14, 1998 covering the offering of up to 1,200,000 
shares of the Company's common stock, par value $.0001 per share (the 
"Shares"). All of the Shares are to be sold by certain stockholders as 
described in the Registration Statement. 

In connection with this opinion, we have examined and relied upon the 
Registration Statement and related Prospectus included therein, the Company's 
Certificate of Incorporation and Bylaws, and the originals or copies 
certified to our satisfaction of such records, documents, certificates, 
memoranda and other instruments as in our judgment are necessary or 
appropriate to enable us to render the opinion expressed below. We have 
assumed the genuineness and authenticity of all documents submitted to us as 
originals, and the conformity to originals of all documents where due 
execution and delivery are a prerequisite to the effectiveness thereof. 

On the basis of the foregoing, and in reliance thereon, we are of the opinion 
that the Shares are validly issued, fully paid and nonassessable. 

We consent to the reference to our firm under the caption "Legal Matters" in 
the Prospectus included in the Registration Statement and to the filing of 
this opinion as an exhibit to the Registration Statement. 

Sincerely, 

Cooley Godward LLP 

/s/ Mark P. Tanoury

Mark P. Tanoury






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