Background. A method that uses single photon emission computed tomography (SPECT) equilibrium radionuclide angiocardiography (ERNA) to measure right ventricular (RV) and left ventricular (LV) volumes (in milliliters) and ejection fraction (EF) is described. Methods and Results. We recorded 35 paired SPECT ERNA and electron beam computed tomography (EBCT) cardiac studies in 27 patients; for comparison with EBCT, a method for measurement of RV and LV volumes and EF with SPECT ERNA was developed in 18 paired studies and was validated and assessed for reproducibility in 17. Validation indicated that SPECT ERNA and EBCT were similar for measurement of RV volume (end-systolic and end-diastolic volumes in a combined analysis) and EF (180 ± 74 mL vs 182 ± 80 mL and 0.44 ± 0.11 vs 0.43 ± 0.11, respectively) and for measurement of LV volume and EF (88 ± 36 mL vs 84 ± 43 mL and 0.53 ± 0.081 vs 0.59 ± 0.07, respectively). The SPECT ERNA method was quite reproducible. Conclusions. RV and LV volumes and EF can be measured readily via SPECT ERNA. Copyright © 2006 by the American Society of Nuclear Cardiology.