To determine the beneficial use of divalproex sodium as a prophylactic treatment for migraine in children. Previous studies for treatment of migraine in adults have shown a greater than 50% reduction in migraine attack frequencies. Few data exist, however, regarding the efficacy and safety of divalproex sodium use in children with migraine. We studied the incidence of headache relief in our patients with migraine aged 16 years and younger treated with divalproex sodium prophylactically at our institution from July 1996 to December 1998 to determine medication dosage used, concomitant headache medications, and possible adverse effects. A total of 42 patients, ranging in age from 7 to 16 years (mean age, 11.3 years), were treated with divalproex sodium for headache. All had a history of migraine with or without aura. Baseline headache frequency during a minimum 6-month period was one to four headaches per month. Divalproex sodium dosage ranged from 15 mg/kg/day to 45 mg/kg/day. Of the 42 patients, 34 (80.9%) successfully discontinued their abortive medications. After 4 months' treatment, 50% headache reduction was seen in 78.5% of patients, 75% reduction in 14.2% of patients, and 9. 5% of patients became headache-free. These results indicate divalproex sodium to be an effective and well-tolerated treatment for the prophylaxis of migraine in children.