Dopaminergic mechanisms have been investigated in post-mortem brain specimens from nineteen patients with schizophrenia and nineteen controls. Dopamine turnover was not increased in schizophrenic patients but, as assessed by the spiroperidol-binding technique, there was a significant increase in postsynaptic receptor sensitivity. The change in the dopamine receptor occurred in nucleus accumbens, putamen, and caudate nucleus. Increased dopamine-receptor sensitivity was present in five patients who had been free of neuroleptic medication for at least 1 year before death, and therefore may be related to the disease process.