Twenty-eight individuals with familial schizophrenia, from 16 unrelated families (12 sibling pairs and 4 individuals whose siblings refused scanning), and 21 normal control subjects were examined by cerebral magnetic resonance imaging (MRI). Measurements of the cerebrum, temporal lobes, and cerebral lateral ventricles were obtained using consecutive coronal sections containing these structures. Temporal lobe volume was significantly decreased by approximately 10% in these early onset schizophrenic siblings compared with normal controls. These findings add to recent post-mortem and neuroradiological evidence for morphological alteration in the temporal lobes in schizophrenia.