55 patients with schizophrenia were divided into three groups according to the clinical symptoms: (1) productive schizophrenias, i.e. patients with hallucinations, catatonic excitation and stupor; (2) paranoia and schizophrenia simplex, and (3) non-productive schizophrenias, i.e. patients with schizophrenic defects and hebephrenia. Total cerebral blood flow (CBF) and the rates of cerebral oxygen, carbon dioxide, glucose and lactate metabolism were investigated. Patients with productive schizophrenias displayed a significant increase in CBF (to an average of 101.4 ml/l00 g min), CMR oxygen (to an average of 6.26 ml/100 g min) and CMR glucose (to an average of 12.11 mg/100 g min), i.e. CBF and CMR oxygen nearly doubled and CMR glucose more than doubled in comparison with normal findings. In patients with paranoia and schizophrenia simplex CBF and oxidative metabolism did not vary much and were within the normal range. Non-productive schizophrenias showed a significant decrease in CBF (to an average of 36.7 ml/100 g min), CMR oxygen (to an average of 2.20 ml/100 g min) and CMR glucose (to an average of 3.86 mg/100 g min) in comparison with both other groups of schizophrenias and the group of healthy young men. The results demonstrated variations in CBF and oxidative metabolism of the brain in patients with distinct types of schizophrenia. It was possible to find a correlation between the mental state of the psychosis on the one hand and CBF and metabolism on the other. The high CBF and metabolic rates of the brain in productive schizophrenias might be due to disturbances in the cerebral metabolism of biogenic amines.