The relationship between cardiac output, total peripheral resistance index (TPRI) treatment, and prognosis was evaluated in 151 patients studied by the Shock Unit of the Detroit General Hospital. Although the hemodynamic values did not correlate with the severity of the shock and did not have a significant effect on the outcome of the patients, the drugs used and the response to treatment were critical. Drugs which maintained or increased any hemodynamic abnormality were detrimental. There was a significant increase in mortality when vasoconstrictor drugs were used in patients who had a low cardiac output (less than 2.5 liters/min/sq m) and were vasoconstricted (TPRI above 2,200 dyne-sec/cm5/sq m). Likewise, the use of vasodilators in septic patients, especially those with the highest cardiac outputs (above 3.5 liters/min/sq m) and most vasodilation (TPRI less than 1,300 dyne-sec/cm5/sq m), was also associated with a significantly increased mortality.