Eighteen outpatients with obsessive-compulsive disorder were treated with either buspirone, a partial serotonin agonist, or clomipramine, a serotonin uptake inhibitor, in a double-blind, random-assignment study. Both drugs led to statistically significant and similar improvements in scores on the Yale-Brown Obsessive-Compulsive Rating Scale and other obsessive-compulsive and depression scales. This preliminary result warrants further exploration with a larger sample and other serotonergic agents.