[en] Right ventricular ejection fraction (RVEF) calculated from ECG-gated steady-state ^81mKr angiocardiography and from ^99mTc first-pass studies were compared in 30 patients using a digital, single crystal, gamma-camera. Despite the two entirely different approaches RVEF valves obtained by the two methods were comparable (r=0.97): the mean absolute difference between the two techniques was 2.5%+/-1.5% and the largest observed absolute difference was 5%. In the absence of an accepted reference method for measuring RVEF, this close correlation provides indirect validation of both techniques. The choice of method will therefore depend on several factors, including radiotracer availability, the characteristics of the gamma-camera and the protocol of clincal investigation. (orig.)