The results of a long-term study of prophylactic treatment of posttraumatic epilepsy performed in Czechoslovakia during the years 1963 through 1980 are reported. The prophylactically treated group of 144 patients with severe brain injuries was compared with a control group of 24 equally damaged cases without prophylactic treatment. The preventive treatment lasting 2 years in the great majority of cases was performed with relatively low doses of phenytoin (160--240 mg/day) and phenobarbital (30--60 mg/day) administered orally. The incidence of late posttraumatic epilepsy was 25% in the control and 2.1% in the prophylactically treated group. Only one patient (0.7%), however, developed seizures during the course of the prophylactic treatment. The efficiency of prophylactic pharmacotherapy has been proved in long-term observations lasting 8 to 13 years.