A total of 96 monotherapies with carbamazepine, phenytoin, phenobarbital or primidone, were analyzed in 42 patients with partial epilepsy. Patients who presented a seizure frequency reduction of 75% or more during the second or third monotherapy, were considered to be improved. Out of the 54 comparisons actuated among these monotherapies, only a scanty percentage of cases, evaluated in 16.7%, presented a significant improvement in seizure frequency. Among non-responding patients, the seizure frequency observed with single monotherapies is practically unchanged, when analyzed with Fischer test.