Attention is called to the various prevailing theories with reference to the pathogenesis of psychosis in patients suffering cardiac failure. The literature is reviewed to indicate widely differing viewpoints.The records of 2293 admissions to a public hospital during the last decade because of cardiac decompensation indicated that 23 patients were treated because of complicating psychosis. Data from these and one additional patient are reviewed.Incidence, sex, age, heart stimulants employed, cardiac complications, hypertension, liver edema, other complicating diseases and course are discussed.Comparatively rare incidence of psychosis in cardiac failure is indicated. Digitalis and other drugs were not found to cause psychosis in this series of patients. Associated syphilitic infection was found in three cases, but, excepting one of these subjects, syphilis apparently could not account for the development of psychosis. Alcoholism was an etiologic factor in one patient's psychosis. The status of arteriosclerosis was found to be inferential; 13, or 54 per cent, of the patients presented clinical signs of cerebral arterial degeneration.However, no one or series of causative factors were noted which were not also observed in the 99 per cent nonpsychotic subjects treated for cardiac decompensation.