Single‐photon emission computed tomography (SPECT) imaging with n‐isopropyl1odoamphetamine (IMP) was performed on 11 patients with bipolar mania, 21 acute schizophrenics, and 15 healthy control subjects. Subjects were evaluated with neuropsychological tests and psychiatnc rating scales. SPECT bram studies were blindly evaluated to assess the degree of radiopharmaceutical uptake in three neuroanatomical regions of interest in each hemisphere. All the control subjects, 1 manic patient and 1 schizophrenic patient had normal brain SPECT uptake patterns. The scans of all others were read as abnormal. Hypofrontality was noted in some schizophrenics and maniacs. A significant increase in tracer uptake in temporal lobes was observed in both patient groups, more prominently in the manic patients. Increased and decreased basal ganglia uptake was also observed in patients. Both manic and schizophrenic patients showed cortical tracer heterogeneity of varying degree. The patterns of cerebral SPECT uptake seen in these acute psychoses were not specific for a diagnosis, but may be associated with dimensions of psychopathology. Because the patterns are different from those seen in cerebrovascular disease and the dementias, they may prove to be helpful in differential diagnosis.