Background: Mounting evidence suggests the involvement of the dopamine system in the pathophysiology of obsessive-compulsive disorder. Method: The relationship of the dopamine D 2 receptor (DRD2) TaqI A, and catechol-O-methyltransferase (COMT) NlaIII High/Low activity polymorphism to obsessive-compulsive disorder (OCD) was examined in a sample of 150 patients and 150 controls. Results: OCD patients did not show significant differences in genotype distribution and allele frequency for polymorphisms investigated relative to controls. However, when the sample was stratified by gender, there was a trend to a significant predominance of the DRD2 A2A2 genotype ( p = 0.049), and a higher frequency of the DRD2 A2 allele ( p = 0.020) and low-activity COMT allele ( p = 0.035) in male OCD patients compared to male controls. In addition, we observed an association of the DRD2 A2A2 genotype in patients with an early onset of disease (V15 years) ( p = 0.033). Conclusions: Our findings replicate previous reports and provide support for a potential role of the COMT and DRD2 locus in subgroup of male, early onset patients with OCD.