Multiple personality disorder is understood today as chronic dissociative psychopathology that most often develops in response to severe abuse in childhood. The dissociative component is a manifestation of a defense mechanism out of control: The person with a biopsychological capacity to dissociate flees inward from overwhelming abuse or feared abuse. When continuing abuse perpetuates dissociations and they are chained by common affective themes, the foundations of multiple personality disorder are laid. Although the disorder has its roots in childhood, most patients are not diagnosed with this condition until 20 to 50 years of age. Many have received several prior, erroneous diagnoses of mental or physical disorders or both over a period of 7 or more years. Failure of diagnosis is an indication of the multiple factors that contribute to making this a covert disorder. Diagnosis and management begin at the same place: the establishment of trust and therapeutic alliance between patient and therapist.