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                                                                     Exhibit 5.1


February 7, 2000




webMethods, Inc.
3877 Fairfax Ridge Road
Fourth Floor
Fairfax, VA 22030

Re:      Registration Statement on Form s-1

Ladies and Gentlemen:


We have furnished this opinion to you in connection with a Registration
Statement on Form S-1 (the "Registration Statement") to be filed with the
Securities and Exchange Commission (the "Commission") under the Securities Act
of 1933, as amended (the "Securities Act"), for the registration of an aggregate
of 4,715,000 shares of Common Stock, $.01 par value per share (the "Shares"), of
webMethods Corporation, a Delaware corporation (the "Company"), of which 615,000
shares are subject to the exercise of an over-allotment option granted by the
Company to the Underwriters).

The Shares are to be sold by the Company pursuant to an underwriting agreement
(the "Underwriting Agreement") to be entered into by and among the Company and
Morgan Stanley & Co. Incorporated, Merrill Lynch, Pierce, Fenner & Smith
Incorporated, Dain Rauscher Incorporated and Friedman, Billings, Ramsey & Co.,
Inc., as representatives of the several underwriters named in such Underwriting
Agreement, the form of which has been filed as Exhibit 1.1 to the Registration
Statement.

We are acting as counsel for the Company in connection with the sale by the
Company of the Shares. We have examined signed copies of the Registration
Statement as filed with the Commission. We have also examined and relied upon
minutes of meetings of the stockholders and the Board of Directors of the
Company as provided to us by the Company, stock record books of the Company as
provided to us by the Company, the Fourth Amended and Restated Certificate of
Incorporation and Bylaws of the Company, each as amended and/or restated to
date, and such other documents as we have deemed necessary for purposes of
rendering the opinions hereinafter set forth.

In our examination of the foregoing documents, we have assumed the genuineness
of all signatures, the authenticity of all documents submitted to us as
originals, the conformity to original documents of all documents submitted to us
as certified photostatic or facsimile

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copies and the authenticity of the original of such latter documents, and legal
capacity of all natural persons.

We assume that the appropriate action will be taken, prior to the offer and sale
of the Shares in accordance with the Underwriting Agreement, to register and
qualify the Shares for sale under all applicable state securities or "blue sky"
laws.

We express no opinion herein as to the laws of any state or jurisdiction other
than the Delaware General Corporation Law Statute, reported judicial decisions
interpreting such statute and applicable provisions of the Constitution of the
State of Delaware, and the federal laws of the United States of America. To the
extent that any other laws govern the matters as to which we are opining herein,
we have assumed that such laws are identical to the state laws of the State of
Delaware, and we are expressing no opinion herein as to whether such assumption
is reasonable or correct.

Based upon and subject to the foregoing, we are of the opinion that the Shares
have been duly authorized for issuance and the Shares, when issued and paid for
in accordance with the terms of the Plans, will be validly issued, fully paid
and nonassessable.

It is understood that this opinion is to be used only solely in connection with
the offer and sale of Shares while the Registration Statement is in effect.

Please note that we are opining only as to the matters expressly set forth in
this letter, and no other opinion should be inferred beyond the matters
expressly stated herein.

We hereby consent to the filing of this opinion with the Commission as an
exhibit to the Registration Statement in accordance with the requirements of
Item 601(b)(5) of Regulation S-K under the Securities Act. In giving such
consent, we do not admit that we are in the category of persons whose consent is
required under Section 7 of the Securities Act or rules and regulations of the
Commission.

Very truly yours,


/s/ Shaw Pittman

Shaw Pittman
A Partnership Including
Professional Corporations