Individuals with obsessive-compulsive disorder (OCD) experience recurrent obsessive and/or compulsive thoughts and behaviours which cause them distress, and significantly impair their daily lives. The disorder is thought to have a chronic course and a low rate of remission, as evidenced by mainly clinical samples. Longitudinal psychiatric epidemiological studies are few and far between. This article presents the findings relating to OCD from one such study, the Zurich Study: OCD defined according to DSM-5 criteria had a high prevalence rate and frequently a chronic course but it had a long-term remission rate of almost 60%, which is higher than hitherto believed. OCD was generally highly comorbid with other disorders and particularly closely associated with social phobia.