Five patients with a manic episode and 7 age-comparable control subjects were studied with single-photon emission computed tomography and [99mTc]d,l-hexamethylpropyleneamine oxime. Manic patients showed significantly lower blood flow in the basal portion of the right temporal lobe compared with normal control subjects. Moreover, manic patients showed a left-right asymmetry (a significantly lower perfusion in the right versus left temporal basal cortex), as well as a dorsal-ventral asymmetry (a significantly lower perfusion in the right temporal basal versus dorsal cortex). These findings suggest that the right basotemporal cortex may play an important role in the production of primary mania.