The authors interviewed 102 individuals with clinical diagnoses of multiple personality disorder at four centres using the Dissociative Disorders Interview Schedule. The patients reported high rates of childhood trauma: 90.2% had been sexually abused, 82.4% physically abused, and 95.1% subjected to one or both forms of child abuse. Over 50% of subjects reported initial physical and sexual abuse before age five. The average duration of both types of abuse was ten years, and numerous different perpetrators were identified. Subjects were equally likely to be physically abused by their mothers or fathers. Sexual abusers were more often male than female, but a substantial amount of sexual abuse was perpetrated by mothers, female relatives, and other females. Multiple personality disorder appears to be a response to chronic trauma originating during a vulnerable period in childhood.