Eleven children with Sydenham's chorea (8 girls and 3 boys, mean age = 8.4 +/- 2.2 [SD] years) underwent comprehensive physical, neuropsychologic, and psychiatric examination. The chorea was manifested as dysarthria, gait disturbances, and frequent adventitious movements of the face, neck, trunk, and extremities. Antineuronal antibodies were present in 10 of 11 children. All children exhibited concomitant psychologic dysfunction, specifically obsessive-compulsive symptomatology, increased emotional lability, motoric hyperactivity, irritability, distractibility, and age-regressed behavior. Obsessive-compulsive symptoms were observed in 9 (82%) children, 4 of whom met diagnostic criteria for obsessive-compulsive disorder. These behavioral symptoms began several days to weeks before the chorea was observed, and they waxed and waned in severity along with the motoric abnormalities. These results suggest that psychologic, particularly obsessive-compulsive, symptoms are accompanying manifestations of Sydenham's chorea which may require medical attention.