To investigate whether gated radionuclide angiographic phase imaging is useful for visually displaying the origin of ventricular premature complexes (VPCs), 82 patients were studied by gating only VPCs. The VPC "origin" by the scintigraphic method was defined as the area of earliest phase and was compared with that predicted by 12-lead electrocardiographic criteria in all patients and to invasive electrophysiologic mapping in 10. Separating the right ventricle into 3 and the left ventricle into 4 segments, the phase imaging method and the electrocardiographic criteria agreed as to ventricle of VPC origin in 69 patients (84%) and segment of origin within each ventricle in 46 (56%). When baseline ventricular wall motion was analyzed, the 2 methods agreed to the ventricle of VPC origin in 31 of 33 patients (94%) with normal wall motion, 20 of 23 (87%) with segmental wall motion abnormalities and 19 of 26 (73%) with diffuse wall motion abnormalities. Agreement between the 2 methods as to specific segmental localization of the arrhythmia focus was noted in 21 of 33 patients (64%) with normal wall motion, 11 of 23 (48%) with segmental wall motion abnormalities and 12 of 26 (46%) with diffuse hypocontractility. In the 10 patients with endocardial mapping studies, the phase imaging technique confirmed the segment of VPC origin in all 10; the electrocardiographic method was accurate in 8. Thus, gated radionuclide angiographic phase imaging methods may be of value in noninvasively defining the origin of spontaneous VPCs. The visual format allows ready interpretation of the arrhythmia origin, and there may be an advantage to this approach over electrocardiographic morphometric criteria.