IN RECENT YEARS many clinicians have become increasingly troubled over reports of sudden unexplained death occurring in psychiatric patients being treated with phenothiazine tranquilizing drugs. Most cases reported are young, in apparent good health, on fairly high doses of one or more of the phenothiazines, and often, in spite of the level of administered dose, difficult to control. Patients may drop to the floor unconscious, in shock or cardiac arrest, and often have severe cardiac arrhythmias; they aspirate food or gastric contents; or they may be found dead in their rooms without signs of an agonal struggle. Generally, autopsies on such patients are not helpful in fixing an anatomic cause of death. Three possible mechanisms for death have been suggested: cardiac arrhythmias and arrest; sudden catastrophic hypotension; and asphyxia due to aspiration. These sudden death reactions are said to be unpredictable and unpreventable.1,2 Relatively few of these cases