Types of seizures, age at onset of epilepsy, preoperative duration of epilepsy, and age at operation were studied in the literature and in 74 patients who underwent unilateral temporal lobe resection in 1960-1969 in Denmark. The medical and surgical series were compared. The age at onset was significantly lower in the surgical series. Prognostically favourable factors were: i) preoperative presence of a single type of seizure; ii) duration of epilepsy of less than 4 years, and in grand mal epilepsy of less than 1 year; iii) operation for epilepsy in or before early adulthood. Prognostically unfavourable factors were i) preoperative presence of grand mal; ii) age at onset of epilepsy or of the first grand mal seizure between 5 and 20 years; iii) preoperative duration of psychomotor epilepsy over 10 years.