In a 12-week open trial, nine outpatients with obsessive-compulsive disorder(OCD) were treated with fluoxetine, a selective serotonin reuptake inhibitor. The overall clinical state was assessed every two weeks until the end of the 12 week using the Yale-Brown Obsessive Compulsive Scale(Y-BOCS), the Clinical Global Impression Scale(CGI) and Hamilton Depression Rating Scale(HAM-D). A significant improvement was found in the symptomatology of patients as measured on Y-BOCS, CGI and HAM-D(p<0.01 respectively). These results reinforce the clinical efficacy of fluoxetine in OCD. However, double-blind clinical trials should be performed to further clarify the efficacy of fluoxetine in OCD.