To characterize the role of cardiac function in septic shock, serial radionuclide cineangiographic and hemodynamic evaluations were done on 20 patients with documented septic shock. Although all patients had a normal or elevated cardiac index, 10 patients had moderate to severe depression of their ejection fraction with values below 0.40. Thirteen of twenty patients survived their episode. Paradoxically, 10 of 13 survivors, but none of the 7 nonsurvivors, had an initial ejection fraction less than 0.40 (p less than 0.005). The mean initial ejection fraction for the survivors was 0.32 +/- 0.04, and their mean end systolic and end diastolic ventricular volumes were substantially increased with a normal stroke volume. The survivors' serial scans showed a gradual return to normal ejection fraction and ventricular volume by 10 days after the onset of shock. Nonsurvivors had normal initial ejection fractions and ventricular volumes that did not change during serial studies.