Oxygen demand-supply relationships in peripheral tissues were studied in 14 patients who had acute myocardial infarction with advanced pump failure. Seven patients with acute myocardial infarction but without pump failure were studied as a control. In all patients, a Swan-Ganz catheter and a radial arterial cannula were inserted for the purpose of hemodynamic monitoring, and arterial and mixed venous blood were sampled. Initially, oxygen delivery (DO<sub>2</sub>) (p < 0.01) was lower, and oxygen extraction ratio (OER) (p < 0.001) and oxygen tension at 50% saturation (P<sub>50</sub>) (p < 0.01) were higher in patients with pump failure than in the controls. During the therapeutic course, with an increase in the cardiac index and DO<sub>2</sub>, oxygen uptake (VO<sub>2</sub>) did not change but OER (p < 0.001) and P<sub>50</sub> (p < 0.01) significantly decreased in 6 survivors with pump failure. In contrast, an increased VO<sub>2</sub> (p < 0.01) and no change of OER and P<sub>50</sub> were observed in 8 non-survivors with pump failure. These results suggest that reversibility of oxygenokinetics might be an important factor for recovery from critical heart failure.