Rheumatic fever (RF) remains a significant public health problem in developing countries. Although its incidence has been declining in developed areas, several outbreaks of RF have been identified in the United States since 1985. To study the prevalence and clinical features of Sydenham's chorea (SC), a well-recognized expression of RF, we examined 50 consecutive patients with RF seen at our Pediatric Cardiology Clinic. Chorea was rated on a scale of 0-4 (0 = no chorea; and 4 = severe chorea, patient unable to walk). Chorea, active or in remission, occurred in 13 patients (26%). The male-to-female ratio was 1.08 among the total population and 0.86 among the SC group. The mean age of the 50 patients at onset of RF was 8.4 years and the standard deviation (SD) 3.1 years. Carditis was diagnosed in 84% of patients with and without chorea, but arthritis was more common in the latter group (83.8%) than in the SC group (30.8%). The mean age at onset of SC was 9.2 years (SD 2.7). Involuntary movement, noticed by nine patients, was the most common initial symptom. Chorea went into remission in eight patients after 9.9 months (SD 13.4). Chorea was rated 3 in ten patients, 1 in two patients, and 4 in one patient. Among the five patients with active SC, three had hemichorea and two had generalized chorea. We recognized abnormal saccades in 80% of patients with active chorea, whereas just 13.5% of patients without chorea displayed this abnormality. SC remains an important cause of chorea in countries plagued by RF.