The Wisconsin Card Sorting Test (WCST) and an alternation learning task were administered to 15 women with obsessive-compulsive disorder (OCD) and 15 age-, sex-, education-, and intelligence-matched healthy controls. OCD patients were significantly slower on the WCST as compared to the controls. Their performance on the alternation learning task was impaired relative to the control group, though this difference was diminished when we used education as a covariate. We found a significant positive correlation between performance on the alternation task and severity of symptoms in the OCD group. Performance of similar alternation tasks is impaired by damage to the orbitofrontal cortex in nonhuman primates. Therefore the data presented support the hypothesis of orbitofrontal cortex dysfunction in OCD.