Combination therapy consisting of high-dose pyridoxal phosphate (40-50 mg/kg/day) and low-dose synthetic ACTH (0.01 mg/kg/day) was prescribed in 28 children with infantile spasms. Monotherapy with pyridoxal phosphate provided excellent seizure control in 3 of the 28 (11%) patients. ACTH was subsequently added to the regimen of the remaining 25 patients. As of 1 month after discontinuing the ACTH treatment, 21 of the 25 (84%) patients had experienced no seizures. The mean interval until seizure control was achieved was 4.1 days after the start of treatment with ACTH. The 21 patients have been monitored for a mean of 34.9 months (range 2-81 months); 6 patients (29%) have had recurrences of infantile spasms, and 10 (48%) have experienced normal development. Fourteen of the 28 patients (50%) have had transient increases in liver enzymes, but none of the patients developed more serious side effects.