Studies of a nonfatal and fatal case of barbiturate poisoning have been used in a discussion of the differential diagnosis of accidental vs intentional barbiturate poisoning. They show that, although cases of accidental barbiturate poisoning do occur, they are not caused by drug automatism. The apparent lack of self-destructive intentionality and the amnesia for the overdosage in nonfatal cases, erroneously diagnosed as drug automatism, are explained by the patients' needs to deny their self-destructiveness and to repress their memory of the overdosage. The literature contains no well-authenticated cases of fatal barbiturate poisoning caused by drug automatism. The persistence of the drug automatism hypothesis is partially explained by the tendency of many patients, their relatives, and physicians to deny the self-destructive motives and actions of the patient.