The effects of alcohol on heart muscle have been explored in numerous studies of normal and diseased humans, intact animals, and isolated animal heart muscle preparations. The results vary according to dose, route, duration, and frequency of administration, parameters measured, and pathologic state of subjects. Most studies indicate that alcohol in sufficient doses decreases myocardial contractility. The dose required for this effect in humans may be lower if there is clinical evidence of heart muscle disease or if the subject has ingested substantial amounts of alcohol for a long time.