[HOGAN & HARTSON L.L.P. LETTERHEAD]



                                 June 1, 2000


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 9,038,411 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 1998 Stock Option and Incentive 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. (S)
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
               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 State of the State
               of Delaware on May 30, 2000 and by the Secretary of the Company
               on the date hereof as being complete, accurate, and in effect.


Board of Directors
VIA NET.WORKS, Inc.
June 1, 2000
Page 2

          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 a
               meeting held on April 14, 1998, as certified by the Secretary of
               the Company on the date hereof as being complete, accurate and in
               effect, relating to the adoption of the Plan.

          6.   Resolutions of the Company's stockholders adopted at an annual
               meeting held on April 6, 1999 and by written consent dated
               February 3, 2000, approving the Plan and an amendment thereto,
               respectively, as certified by the Secretary of the Company on the
               date hereof as being complete, accurate and in effect.

          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.


Board of Directors
VIA NET.WORKS, Inc.
June 1, 2000
Page 3

          We hereby consent to the filing of this opinion letter as Exhibit 5.01
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.