Twenty-five patients with septic shock underwent simultaneous radionuclide ventriculography and right heart catheterization to clarify the role of the right ventricle in this syndrome. A depressed right ventricular ejection fraction (less than 38%) was present in 13 patients and was found in patients with elevated cardiac output (4 of 6 patients) and with normal or low cardiac output (9 of 19 patients). Right ventricular dysfunction was seen with or without acute respiratory failure. In eight patients, a depressed right ventricular ejection fraction was seen in combination with an abnormal left ventricular ejection fraction (less than 48%), but in five patients, right ventricular ejection fraction impairment occurred with normal left ventricular ejection fraction. There was no significant correlation between abnormal right ventricular afterload and depressed right ventricular ejection fraction. No clinical or hemodynamic finding could be used to identify patients with diminished right ventricular ejection fraction. On follow-up study in 17 surviving patients, right ventricular ejection fraction improved in 6 and was unchanged in 11. Improvement in right ventricular ejection fraction occurred more frequently in patients without pulmonary hypertension or respiratory distress. The results suggest that right ventricular dysfunction in septic shock may be more common than previously suspected. It may be caused by abnormalities in right ventricular afterload in some patients and depressed myocardial contractility in others. The findings are of therapeutic importance since interventions that diminish right ventricular afterload and increase right ventricular contractility would be appropriate in patients with septic shock and right ventricular dysfunction.