There is increasing evidence that the aetiology of obsessive-compulsive disorder (OCD) has a marked genetic component, although the precise mechanism of inheritance is unclear. Clinical and pharmacological studies have implicated the serotonergic and dopaminergic systems in disease pathogenesis. This study investigated the role of attractive candidate genes in the serotonergic and dopaminergic pathways in the development of OCD. The distribution of selected polymorphic variants in the serotonin receptor type 2A and 1Dbeta (5-HT(2A), 5-HT(1Dbeta)), dopamine transporter (DAT), dopamine receptor type 4 (DRD4) and monoamine-oxidase A (MAO-A) genes were analysed in 71 OCD cases and 129 control individuals in the genetically homogeneous Afrikaner population, by means of case-control association studies. Although no statistically significant genotypic or allelic associations were detected, the data yielded interesting preliminary results that warrant further discussion and investigation.