Exhibit 23.3
                                                                    ------------

CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

As independent public accountants, we hereby consent to the incorporation by
reference in this registration statement on Form S-8 of our report dated
February 19, 1999 (except with respect to the matters discussed in Note 15 to
the consolidated financial statements, as to which the date is May 16, 1999)
included in CAIS Internet, Inc.'s registration statement on Form S-1 (File No.
333-72769) and to all references to our Firm included in this registration
statement.

                               /s/ Arthur Andersen LLP

Vienna, Virginia
February 29, 2000