Hemodynamic studies have shown that shock following myocardial infarction is caused primarily by sudden reduction in cardiac output to one-half of normal values, with unimportant changes in total blood volume. A high mortality accompanies this condition. Treatment of heart block and ventricular tachycardia associated with shock can result in dramatic improvement. Morphine, oxygen and digitalis are considered routine treatment, and morphine alone may reverse hypotension without true cardiogenic shock. Although vasopressor agents may produce subjective improvement, in the author's experience they did not decrease the ultimate mortality. Hypothermia and assisted circulation as therapeutic measures are currently in the experimental stage.