gamma-Aminobutyric acid (GABA) levels in CSF were not significantly different in 30 drug-free schizophrenic patients and in 39 normal control subjects, because the control subjects were significantly older. Schizophrenic women had significantly lower levels than age-matched normal control women (less than 30 years). The GABA levels increased with duration of illness, number of hospitalizations, and months of hospitalizations, as well as with age. They correlated nonsignificantly with psychosis levels. After short-term pimozide treatment, GABA levels in all patients were raised, albeit nonsignificantly. The date suggest that low GABA levels may be observed only in the early years of the illness, particularly in female schizophrenic patients, and that these levels increase with time and with long-term neuroleptic treatment.