96 monotherapies with carbamazepine, phenytoin, phenobarbital and primidone were assessed in 42 patients with partial epilepsy. Those whose seizure frequency was reduced by 75% or more were considered to have improved. In 54 comparisons of monotherapies significant improvement in seizure frequency was achieved in only 16.7% of cases. Nonresponding patients showed practically no change across all comparisons according to the Fischer test.