In a double-blind trial, children who had recurrent and/or complex febrile convulsions were treated with either phenobarbital sodium or carbamazepine. Forty children were suitable for analysis; 19 were receiving carbamazepine, and 21 were receiving phenobarbital. Of the carbamazepine-treated patients, nine (47%) had recurrent convulsions despite therapeutic levels of the drug, while only two (10%) of the phenobarbital-treated patients suffered further seizures. These results confirm previous findings suggesting that carbamazepine is not as effective in the prophylactic treatment of febrile convulsions as phenobarbital.