Background: Sydenham's chorea is still the most frequently seen form of acquired chorea in childhood in developing world despite the use of antibiotics. It is a debilitating illness lasting for weeks or months and requires drug therapy. Objective: To evaluate and compare the efficacies of sodium valproate and carbamazepine in the treatment of the choreiform movements in Sydenham's chorea. Design: A prospective trial carried out with 24 children with Sydenham's chorea. Patients: Twenty-four patients were divided into two groups having similar demographic and clinical properties. One group (n = 17) was given carbamazepine (15 mg/kg per day) and the other (n = 7) was given sodium valproate (20-25 mg/kg per day). As soon as the symptoms were taken under control, doses of the drugs were tapered slowly. The duration of the drug use was recorded. The time of response to therapy was compared between the groups and the patients were monitored for the adverse effects. Results: There was no significant difference between the groups with respect to the time of clinical improvement and time of complete remission, duration of the therapy and the recurrence rates. Clinical improvement began by 8.0 +/- 4.0 days in sodium valproate and 7.4 +/- 8.2 days in carbamazepine group (P = 0.88). In the whole group no adverse effect was seen due to the drugs. Conclusion: Carbamazepine and valproic acid are equally effective and safe drugs in the treatment of choreiform movements in Sydenham chorea. (C) 2002 Elsevier Science B.V. All rights reserved.