The aim of this study was to compare the efficacy, safety, and tolerability of sertraline and clomipramine in the treatment of obsessive-compulsive disorder (OCD). Outpatients with DSM-III-R defined OCD for 1 year or longer and scores of >/=20 on the YaleBrown Obsessive Compulsive Scale (Y-BOCS), >/=7 on the National Institute of Mental Health Global Obsessive-Compulsive Scale (NIMH-OC), >/=4 on the Clinical Global Impression Severity of Illness Scale (CGI-S) and