Changes in the major parameters of central and intracardiac hemodynamics and body's oxygen supply were examined in 93 patients with massive myocardial infarction in the in-hospital period of the disease. Traditional therapy was given to 71 patients; in addition, phosphocreatine infusions (a course dose being 30 g) were used in 22 patients in acute myocardial infarction. Phosphocreatine therapy failed to substantially affect cardiac pump function, but prevented left ventricular dilation and development of congestive heart failure. The patients receiving phosphocreatine showed an increase in body's oxygen consumption due to its elevated tissue extraction. No adverse effects of phosphocreatine were found.