Objective: The purpose of this study was to assess the efficacy of fluoxetine, a selective serotonergic antidepressant, in the treatment of dysthymia. Method: Thirty-five patients who met criteria for dysthymia, but not major depression, began randomized, double-blind 8-week trials of fluoxetine or placebo. Results: Of 32 patients who completed the study, 10 (62.5%) of the 16 patients given fluoxetine and three (18.8%) of the 16 given placebo responded to treatment. Response was defined as 1) 50% or greater decrease in Hamilton Rating Scale for Depression score and 2) a score of 1 or 2 on the Clinical Global Impression (CGI) improvement subscale. Fluoxetine subjects showed significantly greater improvement at week 8 than placebo subjects on the Hamilton depression and CGI scales, but not on the Hopkins Symptom Checklist (58-item) or the cornell Dysthymia Rating Scale. Conclusions: When compared to placebo, fluoxetine showed short-term effectiveness in treating dysthymic symptoms.