Joint Filing Agreement

                                    Exhibit 1
                                    ---------

                             Joint Filing Agreement

     The undersigned hereby agree that the statement on Schedule 13D filed by
the undersigned with respect to the Common Stock of Micro Therapeutics, Inc. is,
and any amendment thereto signed by each of the undersigned shall be, filed on
behalf of each undersigned pursuant to and in accordance with the provisions of
Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended.

Dated: June 4, 2001                     MICRO INVESTMENT, LLC

                                        By: Warburg, Xxxxxx Equity Partners,
                                            L.P., Managing Member

                                        By: Warburg, Xxxxxx & Co.,
                                            General Partner

                                        By: /s/ Xxxxx X. Xxxxxxx
                                            ------------------------------
                                        Name:  Xxxxx X. Xxxxxxx
                                        Title: Attorney-in-Fact


Dated: June 4, 2001                     WARBURG, XXXXXX EQUITY
                                        PARTNERS, L.P.

                                        By: Warburg, Xxxxxx & Co.,
                                            General Partner

                                        By: /s/ Xxxxx X. Xxxxxxx
                                            ------------------------------
                                        Name:  Xxxxx X. Xxxxxxx
                                        Title: Attorney-in-Fact


Dated: June 4, 2001                     WARBURG, XXXXXX & CO.

                                        By: /s/ Xxxxx X. Xxxxxxx
                                            ------------------------------
                                        Name:  Xxxxx X. Xxxxxxx
                                        Title: Attorney-in-Fact


Dated: June 4, 2001                     WARBURG PINCUS LLC

                                        By: /s/ Xxxxx X. Xxxxxxx
                                            ------------------------------
                                        Name:  Xxxxx X. Xxxxxxx
                                        Title: Vice President and General
                                               Counsel






Dated: June 4, 2001                     VERTICAL FUND ASSOCIATES, L.P.

                                        By: The Vertical Group, L.P.,
                                            General Partner

                                        By: /s/ Xxxx X. Xxxxxxxx
                                            ------------------------------
                                        Name:  Xxxx X. Xxxxxxxx
                                        Title: General Partner


Dated: June 4, 2001                     VERTICAL LIFE SCIENCES L.P.

                                        By: The Vertical Group, L.P.,
                                            General Partner

                                        By: /s/ Xxxx X. Xxxxxxxx
                                            ------------------------------
                                        Name:  Xxxx X. Xxxxxxxx
                                        Title: General Partner