Some studies suggest a relationship between obsessive-compulsive disorder (OCD) and Gilles de la Tourette's syndrome. The pathophysiology of the latter may involve the dopamine system. We screened three important exons of the dopamine D2 receptor (DRD2) gene for mutations in a group of OCD patients with or without tics. No structural changes were found, suggesting no relationship between DRD2 and OCD. Moreover, the frequency of the polymorphism in exon 6 was different from that found in schizophrenics.