The question of whether organic conditions, such as complex partial seizures, can cause dissociative symptoms is controversial. Although a diagnostic category for organic dissociation is included in the tenth edition of International Classification of Disease, it has never been identified in the Diagnostic and Statistical Manual. Its inclusion in the upcoming DSM-IV is currently under debate. This article surveys representative literature regarding the role of organic factors in the causation of dissociative symptoms and considers the differential diagnosis of organic dissociation from current and historic perspectives. Dissociative symptoms and disorders (including amnesia, fugue, depersonalization, multiple personality, automatisms, and certain furors) can be induced by a variety of medications, drugs of abuse, and medical illnesses or conditions affecting cerebral function. Organic dissociation can be distinguished from intoxication, amnestic disorder, and delirium. Psychiatric nosology and our conceptualization of altered mental states and functions would benefit from use of the concept of an organic dissociative syndrome, which has clinical, neurophysiologic, and medicolegal significance. Such a category should be included in DSM-IV.