OBJECTIVE: The tic-related subtype of obsessive-compulsive disorder (OCD) has a distinct clinical profile. The course of tic-related OCD has previously been investigated in treatment studies, with inconclusive results. This study aimed to compare clinical profiles between tic-related and tic-free OCD patients and to establish the influence of tics on the 2-year natural course in adult OCD patients. METHODS: Within the Netherlands OCD Association cohort, 377 patients with a current DSM-IV diagnosis of OCD were divided into a tic-related group (28%) and a tic-free group and compared on clinical variables with t tests or χ² tests. Linear mixed-model analyses were used to compare the 2-year course between the groups, with the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) as primary outcome measure. Data were collected from 2005 to 2007 and from 2007 to 2009. RESULTS: Compared to patients with tic-free OCD, those with tic-related OCD reported earlier disease onset (P = .009) and more symmetry/ordering symptoms (P = .002). Overall symptom severity was similar in both groups. Patients with tic-related OCD reported increased traits of attention-deficit hyperactivity (P