Asymmetries of the brain have been known about for at least a century, but they have been explored in detail only relatively recently. It has become clear that, although different asymmetries are common throughout the animal kingdom, they are most marked in the human brain. Disturbances in asymmetry are particularly striking in patients with schizophrenia and perhaps all psychotic illnesses, and may provide the neurological substrate for the etiology and clinical manifestations of the illness.