The clinical features of refractory epilepsy were studied in comparison between 135 patients in a refractory group and 103 in a controlled group. All the children were Japanese. The clinical features of the refractory group were the onset of epilepsy during the first year of life, absence of family history, retarded development before the onset, phakomatoses, daily or weekly seizures, secondarily generalized epilepsy, and marked EEG abnormalities at the initial visit, a change of types in epilepsy, no improvement in EEG findings, mental deterioration or severe retardation during the follow-up. The number of drugs was increased and relatively new drugs such as carbamazepine, valproic acid or clonazepam were frequently administered. The side effects, including gum hypertrophy, drowsiness, hypertrichosis, ataxia or increased serum-GTP, were more frequent in the refractory group.