Obsessive-compulsive disorder (OCD) is a chronic, distressing illness that is associated with a specific and unique response to selective serotonin reuptake inhibitors. Escitalopram was granted marketing authorization for the treatment of OCD from the European authorities in 2007 based on results from two Phase-III clinical trials in patients with moderate-to-severe OCD. One, a relapse prevention study, demonstrated substantial efficacy of escitalopram 10-20 mg/day in both acute and maintenance treatment, and the other demonstrated superior efficacy and favorable tolerability of escitalopram compared with placebo during 24-week, double-blind treatment. These data, and other studies reviewed here, suggest that escitalopram is an important additional tool for the treatment of OCD.