Many benzodiazepines used as anticonvulsants have nitrogen radicals in positions 1 and 4. Clobazam has nitrogen radicals in positions 1 and 5. We studied the antiepileptic effect of clobazam in 36 patients with intractable epilepsies in childhood. Their ages were 1 year 1 month to 16 years 5 months (mean 8 years). The mean initial dose was 0.33 mg/kg of daily doses and increased up to 0. 71 mg/kg. Nine cases (primary generalized epilepsy 2/2, secondary generalized epilepsy 7/29) were completely free from seizures, and another 9 (secondary generalized epilepsy 8/29, partial epilepsy 1/5) experienced a decrease of 50% or more in seizure frequency. Seizure frequency did not change in 16, and increased in the other 2 (secondary generalized epilepsy 2/29). The antiepileptic effects were observed on the first day to 10th day after clobazam treatment. There were recurrences of seizures in 4 out of 9 patients with complete control of seizures, 1 month later in 3 and 10 months later in one. Mean serum clobazam level of 7 improved cases was 73 ng/ml and that of 3 cases with no response was 94 ng/ml. Although mild clinical side effects such as drowsiness were observed transiently in 17 cases, no abnormality was found in laboratory investigations performed.