Because myocardial dysfunction may result from severe trauma, the author assessed, prospectively, left and right ventricular function in 25 patients who had sustained severe trauma, including blunt chest injury, by electrocardiographically gated blood pool radionuclide angiography. Focal abnormalities of ventricular wall motion were defined in 17 patients: right ventricular in 12, left ventricular in 2 and biventricular in 3. Traumatic tricuspid insufficiency demonstrated in two patients was subsequently verified by contrast angiography. Other means of detecting myocardial contusion (enzymatic, electrocardiographic and scintigraphic) proved to be insensitive when compared with radionuclide angiography. Two of the five deaths were attributed to refractory arrhythmias. Surgical or autopsy evidence of traumatic myocardial injury was obtained in five instances when radionuclide angiography indicated contusion. Of the 13 patients available for follow-up, 11 showed complete or partial resolution of the ventricular wall abnormality and in 2 there was no change. Comprehensive cardiopulmonary monitoring revealed an inverse relation between the right ventricular ejection fraction and pulmonary vascular resistance as well as between the pulmonary vascular resistance and left ventricular ejection fraction and left ventricular end-diastolic volume. Further, as the right ventricular end-diastolic volume was increased in trauma, left ventricular function and compliance were reduced. In blunt chest trauma, right ventricular contusion occurs more frequently than has been recognized previously and positive radionuclide angiography constitutes prima facie evidence of direct myocardial injury. Moreover, left ventricular function remains preload-dependent, but may be depressed by elevated pulmonary vascular resistance, impeding the blood flow from the right to left ventricle, and decreased left ventricular compliance, or both.