Exhibit 5.1


                             HOGAN & HARTSON, L.L.P
                                 COLUMBIA SQUARE
                           555 THIRTEENTH STREET, N.W.
                           WASHINGTON, D.C. 20004-1109
                                 (202) 637-5600
                                 (202) 637-5910


                                 August 31, 2001


Board of Directors
VIA NET.WORKS, Inc.
12100 Sunset Mills Road, Suite 110
Reston, Virginia  20190

Ladies and Gentlemen:

     We are acting as counsel to VIA NET.WORKS, Inc., a Delaware corporation
(the "Company"), in connection with its registration statement on Form S-8 (the
"Registration Statement"), filed with the Securities and Exchange Commission
relating to up to 214,517 newly issued shares of the Company's common stock, par
value $.001 per share (the "Shares"), issuable in connection with the Company's
Amended & Restated Key Employee Equity Plan (the "Plan"). This opinion letter is
furnished to you at your request to enable you to fulfill the requirements of
Item 601(b)(5) of Regulation S-K, 17 C.F.R. ss. 229.601(b)(5), in connection
with the Registration Statement.

     For purposes of this opinion letter, we have examined copies of the
following documents:

     1. An executed copy of the Registration Statement.

     2. A copy of the Plan, as certified by the Secretary of the Company on the
        date hereof as being complete, accurate, and in effect.

     3. The Amended and Restated Certificate of Incorporation of the Company, as
        certified by the Secretary of the Company on the date hereof as being
        complete, accurate, and in effect.


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     4. The Bylaws of the Company, as certified by the Secretary of the Company
        on the date hereof as being complete, accurate, and in effect.

     5. Resolutions of the Board of Directors of the Company adopted at meetings
        held on November 14, 1998, September 28, 1999, January 14, 2000, and
        August 9, 2001, as certified by the Secretary of the Company on the
        date hereof as being complete, accurate and in effect, relating to the
        adoption of, and amendments to, the Plan.

     In our examination of the aforesaid documents, we have assumed the
genuineness of all signatures, the legal capacity of all natural persons, the
accuracy and completeness of all documents submitted to us, the authenticity of
all original documents, and the conformity to authentic original documents of
all documents submitted to us as copies (including telecopies). This opinion
letter is given, and all statements herein are made, in the context of the
foregoing.

     This opinion letter is based as to matters of law solely on the Delaware
General Corporation Law, as amended. We express no opinion herein as to any
other laws, statutes, ordinances, rules, or regulations. As used herein, the
term "Delaware General Corporation Law, as amended" includes the statutory
provisions contained therein, all applicable provisions of the Delaware
Constitution and reported judicial decisions interpreting these laws.

     Based upon, subject to and limited by the foregoing, we are of the opinion
that, when issued in accordance with the terms of the Plan, the Shares will be
validly issued, fully paid and nonassessable.

     This opinion letter has been prepared for your use in connection with the
Registration Statement and speaks as of the date hereof. We assume no obligation
to advise you of any changes in the foregoing subsequent to the delivery of this
opinion letter.


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     We hereby consent to the filing of this opinion letter as Exhibit 5.1 to
the Registration Statement. In giving this consent, we do not thereby admit that
we are an "expert" within the meaning of the Securities Act of 1933, as amended.

                                             Very truly yours,

                                             /s/ Hogan & Hartson L.L.P.

                                             HOGAN & HARTSON L.L.P.