This study introduces a new method for calculating actual left ventricular volumes and cardiac output from data recorded during a single transit of a radionuclide bolus through the heart, and describes in detail current radionuclide angiocardiography methodology. A group of 64 healthy adults with a wide age range were studied to define the normal range of hemodynamic parameters determined by the technique. The normal radionuclide cardiac index averaged 3.25 +/- 0.75 liters/min/m2, the end-diastolic volume index was 62 +/- 16 ml/m2, the stroke volume index was 40 +/- 9 ml/m2, and the ejection fraction was 0.66 +/- 0.07. Radionuclide angiocardiograms were performed in patients undergoing cardiac catheterization to validate the measurements. In 33 patients studied by both techniques on the same day, a close correlation was documented for measurement of ejection fraction (r = 0.89) and end-diastolic volume (r = 0.89). Determination of the linear regression equation for the end-diastolic volumes obtained by the two methods (EDVcath = 1.26 x EDVRN - 7.56) permitted correction of end-diastolic volume and provided an approach for calculation of stroke volume and cardiac output. To validate the method of volumetric cardiac output calculation, 33 simultaneous radionuclide and indocyanine green dye determinations of cardiac output were performed in 18 normal young adults and correlated closely over a range of 4-17 liters/min (r = 0.94). These independent comparisons of radionuclide measurements with two separate methods document that initial transit radionuclide angiocardiography accurately assesses left ventricular function.