This study will compare the effectiveness of combination therapy with the drugs amitriptyline and fluoxetine (AM+FL) and amitriptyline (AM) alone in the treatment of people with fibromyalgia. Doctors will treat each study participant with both AM + FL and AM alone for 6 weeks at a time. The study uses a method that combines results from treatment of individual patients to assess overall treatment effectiveness and help individual patients and their physicians with their treatment decisions. This study will also help compare the results of community-based studies (studies involving private doctors) and studies based at clinical research centers.