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                      [LETTERHEAD OF THE BISYS GROUP, INC.]


                                                                     EXHIBIT 5.1

                                           June 1, 2001


The BISYS Group, Inc.
150 Clove Road
Little Falls, New Jersey  07424

                  Re:      The BISYS Group Inc.'s Registration Statement on Form
                           S-3

Ladies and Gentlemen:

                  I am the Executive Vice President and General Counsel of The
BISYS Group, Inc., a Delaware corporation (the "Company"), and am acting as
counsel in connection with its filing with the Securities and Exchange
Commission (the "Commission") of a registration statement on Form S-3 (the
"Registration Statement"), with respect to the registration under the
Securities Act of 1933, as amended (the "Securities Act"), of $300,000,000
aggregate principal amount at maturity of its 4% Convertible Subordinated Notes
due 2006 (the "Securities"), and shares of the Company's common stock, par value
$0.02 per share (the "Shares"), issuable upon conversion of the Securities
pursuant to that certain indenture, dated as of March 13, 2001 (the
"Indenture"), between the Company and Chase Manhattan Trust Company, National
Association, as trustee. The Company issued the Securities pursuant to that
certain purchase agreement, dated as of March 7, 2001, by and between the
Company and Bear, Stearns & Co. Inc. and Credit Suisse First Boston Corporation,
as initial purchasers (the "Purchase Agreement"). The Securities and the Shares
are to be offered and sold by certain securityholders of the Company.

                  This opinion is being furnished in accordance with the
requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.

                  In connection with this opinion, I have examined originals or
copies, certified or otherwise identified to my satisfaction, of the
Registration Statement, the Indenture and the Purchase Agreement. I have also
examined originals or copies, certified or otherwise identified to my
satisfaction, of such records of the Company and such agreements, certificates
of public officials, certificates of officers or other
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The BISYS Group, Inc.
June 1, 2001

representatives of the Company and others, and such other documents,
certificates and records as I have deemed necessary or appropriate as a basis
for the opinions set forth herein.

                  In my examination, I have assumed the legal capacity of all
natural persons, the genuineness of all signatures, the authenticity of all
documents submitted to me as originals, the conformity to original documents of
all documents submitted to me as certified or photostatic copies and the
authenticity of the originals of such latter documents. In making my examination
of executed documents, I have assumed that the parties thereto, other than the
Company, had the power, corporate or other, to enter into and perform all
obligations thereunder and have also assumed the due authorization by all
requisite action, corporate or other, and the execution and delivery of such
documents by the parties to such documents, and the validity and binding effect
thereof. As to any facts material to the opinions expressed herein which I did
not independently establish or verify, I have relied upon oral or written
statements and representations of officers and other representatives of the
Company and others.

                  I am admitted to the bars in the States of New York and New
Jersey and do not express any opinion as to the laws of any other jurisdiction.

                  Based upon and subject to the limitations, qualifications,
exceptions and assumptions set forth above, I am of the opinion that:

                  1. The Securities have been duly authorized and are valid and
binding obligations of the Company, enforceable against the Company in
accordance with their terms, except to the extent enforcement thereof might be
limited by (i) bankruptcy, insolvency, reorganization, moratorium, fraudulent
conveyance or other similar laws affecting creditor's rights generally, and (ii)
general principles of equity, regardless of whether enforceability is considered
in a proceeding at law or equity.

                  2. The Shares initially issuable upon conversion of the
Securities have been duly authorized and reserved for issuance and, when issued
and delivered upon such conversion pursuant to the terms of the Indenture, will
be validly issued, fully paid and non-assessable.
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The BISYS Group, Inc.
June 1, 2001

                  I hereby consent to the filing of this opinion with the
Commission as an exhibit to the Registration Statement. I also consent to the
reference to the use of my name under the caption "Legal Matters" in the
Registration Statement. In giving this consent, I do not thereby admit that I am
included in the category of persons whose consent is required under Section 7 of
the Securities Act or the rules and regulations of the Commission.


                                       Very truly yours,

                                       /s/ Kevin J. Dell
                                       -----------------------------------------

                                       Kevin J. Dell, Esq.
                                       Executive Vice President and
                                               General Counsel