February 9, 2000



Board of Directors
VIA NET.WORKS, Inc.
12100 Sunset Hills Road
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-1, as amended (the "Registration Statement"), filed with the Securities
and Exchange Commission relating to the proposed public offering of up to
17,000,000 shares of the Company's common stock, par value $.001 per share, all
of which shares (the "Shares") are to be sold by the Company.  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.   The Amended and Restated Certificate of Incorporation of the
               Company, as certified by the Secretary of the Company on the date
               hereof as having been filed with the Secretary of State of the
               State of Delaware on February 8, 2000.

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

          4.   The proposed form of Underwriting Agreement between the Company
               and the several Underwriters to be named therein, for whom
               Donaldson, Lufkin & Jenrette Securities Corporation, Morgan
               Stanley & Co. Incorporated, Salomon Smith Barney Inc. and


Board of Directors
VIA NET.WORKS, Inc.
February 9, 2000
Page 2


               DLJdirect Inc. will act as representatives, and between the
               Company and the several International Managers to be named
               therein, for whom Donaldson, Lufkin & Jenrette International,
               Morgan Stanley & Co. International Limited, Salomon Brothers
               International Limited, Cazenov & Co. and Mees Pierson N.V. will
               act as representatives, filed as Exhibit 1.01 to the Registration
               Statement (the "Underwriting Agreement").

          5.   The proposed form of purchase agreement between the Company and
               certain stockholders relating to the sale by the Company to such
               stockholders of 700,000 Shares (the "Purchase Agreement").

          6.   Resolutions of the Board of Directors of the Company adopted at a
               meeting held on January 14, 2000, as certified by the Secretary
               of the Company on the date hereof as being complete, accurate,
               and in effect, relating to the issuance and sale of the Shares
               and arrangements in connection therewith.

          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.  We express no opinion herein as to any other
laws, statutes, ordinances, rules, or regulations.

          Based upon, subject to and limited by the foregoing, we are of the
opinion that following (i) final action of the Finance Committee of the Board of
Directors of the Company approving the price of the Shares, (ii) execution and
delivery by the Company of the Underwriting Agreement and the Purchase
Agreement, (iii) effectiveness of the Registration Statement, (iv) issuance of
the Shares pursuant to the terms of the Underwriting Agreement and the Purchase
Agreement, and (v) receipt by the Company of the consideration for the Shares


Board of Directors
VIA NET.WORKS, Inc.
February 9, 2000
Page 3


specified in the resolutions of the Board of Directors and the Finance Committee
referred to above, 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.

          We hereby consent to the filing of this opinion letter as Exhibit 5.01
to the Registration Statement and to the reference to this firm under the
caption "Legal Matters" in the prospectus constituting a part of 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.