A group of 27 patients with various types of epilepsy were selected for a 6 mo. double-blind crossover study to compare the anticonvulsant effect and toxicity of eterobarb and phenobarbital. No statistically significant differences in seizure frequency were found among the 21 patients who completed the 6 mo. trial, but 3 others, in whom status epilepticus developed during the crossover from eterobarb to phenobarbital, had to be removed from the trial. When eterobarb and phenobarbital were used in high dosage with corresponding high serum barbiturate levels (over 30 .mu.g/ml), eterobarb appeared to have superior therapeutic effect. Side effects from both drugs included tiredness, sleepiness, nystagmus and infrequently ataxia, but serious systemic toxicity did not occur. Eterobarb is a safe and potent anticonvulsant comparable in efficacy to phenobarbital, and appears to be an effective alternative anticonvulsant.