Vasopressin and oxytocin seem to be involved in the processes of learning and memory in animals and probably in man. These peptides appear to have opposite effects in that vasopressin improves memory processes and oxytocin produces amnestic effects. We measured these neuropeptides in the cerebrospinal fluid of schizophrenic patients with and without neuroleptic treatment, psychiatrically healthy controls and drug-free patients before and after three weeks' neuroleptic treatment. There were no significant differences in vasopressin concentrations between schizophrenics and controls. No influence of neuroleptic treatment on vasopressin concentrations was detected. In contrast, concentrations of oxytocin were increased in all schizophrenic patients and were higher in those receiving neuroleptic treatment. In addition, oxytocin concentrations increased after three weeks' neuroleptic treatment. Drug-induced increase of oxytocin concentrations may be of significance in the clinically observed amnestic syndromes and debilitation in schizophrenics treated with neuroleptics.