To study the clinical phenomenology of multiple personality, 50 consecutive patients with DSM-III multiple personality disorder were assessed using clinical history, psychiatric interview, neurological examination, electroencephalogram, MMPI, intelligence testing, and a variety of psychiatric rating scales. Results revealed that patients with multiple personality are usually women who present with depression, suicide attempts, repeated amnesic episodes, and a history of childhood trauma, particularly sexual abuse. Also common were headaches, hysterical conversion, and sexual dysfunction. Intellectual level varied from borderline to superior. The MMPI reflected underlying character pathology in addition to depression and dissociation. Significant neurological or electroencephalographical abnormalities were infrequent. These data suggest that the etiology of multiple personality is strongly related to childhood trauma rather than to an underlying electrophysiological dysfunction.