Joint Filing Agreement

                                                                       EXHIBIT 4

                             Joint Filing Agreement

     The undersigned hereby agree that the statement on Schedule 13D with
respect to the shares of Common Stock of Coventry Health Care, 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 13d-1(k)
under the Securities Exchange Act of 1934, as amended.


Dated: May 11, 2000                     WARBURG, XXXXXX VENTURES, L.P.

                                        By: Warburg, Xxxxxx & Co.,
                                            General Partner

                                        By: /s/ Xxxxxxx Xxxxxxx
                                            ------------------------------
                                            Partner


Dated: May 11, 2000                     WARBURG, XXXXXX & CO.

                                        By: /s/ Xxxxxxx Xxxxxxx
                                            ------------------------------
                                            Partner


Dated: May 11, 2000                     X.X. XXXXXXX, XXXXXX & CO., LLC

                                        By: Warburg, Xxxxxx & Co.,
                                            General Partner

                                        By: /s/ Xxxxxxx Xxxxxxx
                                            ------------------------------
                                            Partner


Dated: May 11, 2000                     WARBURG, XXXXXX EQUITY PARTNERS, L.P.

                                        By: Warburg, Xxxxxx & Co.,
                                            General Partner

                                        By: /s/ Xxxxxxx Xxxxxxx
                                            ------------------------------
                                            Partner

Dated: May 11, 2000                     By: /s/ Xxxx Xxxxxxxx
                                            ------------------------------
                                            Name: Xxxx Xxxxxxxx
                                                  Trustee


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Dated: May 11, 2000                     By: /s/ Xxxxxxx Xxxxxxx
                                            ------------------------------
                                            Name: Xxxxxxx Xxxxxxx
                                                  Trustee


Dated: May 11, 2000                     By: /s/ Xxxxxxxx Xxxx
                                            ------------------------------
                                            Name: Xxxxxxxx Xxxx
                                                  Trustee


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