Psychiatric disorders were investigated in 74 patients with drug-resistant temporal lobe epilepsy (complex partial epilepsy). In all cases unilateral anterior temporal lobectomy had been performed during the period 1960-69. At follow-up in 1970-71, 45 patients were free from seizures, and in a further group of 15 patients seizure frequency had been substantially reduced. There were four postoperative deaths. Six patients were psychiatrically normal and had no history of any such disorder. Behavioural disturbances were observed in 55 patients. Before operation 11 patients displayed schizophrenia-like psychoses, and nine others became psychotic during follow-up. Fourteen patients attempted suicide on one or more occasions. Half the patients had diminished sexual drive. Improvement in psychiatric status was clearly correlated with relief from seizures and, in those cases with only a few or no seizures after operation, led directly to social rehabilitation. The presence or absence of a psychiatric disorder was not useful as a criterion for or against surgery.