During a 14 month period autopsies were performed on 107 patients with coronary heart disease and the results were evaluated prospectively with special reference to right ventricular infarction. A total of 214 regional infarcts were found, 107 (50%) of which involved the right ventricle. Right ventricular infarction was found in 90 hearts (84%), but only three isolated right ventricular infarcts were seen. Right ventricular involvement was found with equal frequency in anterior and posterior infarction (64 versus 66%), but posterior right ventricular infarcts were much larger (15% of the right ventricle was infarcted versus 1%). Proximal right coronary artery occlusion caused larger right ventricular infarction than did distal occlusion (15 versus 5 g). Right ventricular infarct size was not influenced by coronary artery disease (evaluated angiographically) in noninfarct-related vessels. Anterior right ventricular infarcts were predominantly located near the apex of the heart (to the left of the sternum), whereas posterior right ventricular infarcts were located near the atrioventricular groove (along the right sternal border). Infarct size was equal in patients who died from a first acute anterior or posterior infarct. However, posterior infarcts had more right ventricular involvement (28% of total infarct size versus 7% in anterior infarcts) leaving more of the left ventricular myocardium intact (79 versus 64%). These differences in infarct topography may explain why right ventricular involvement seldom is diagnosed clinically in patients with anterior infarction, and why left ventricular function and prognosis usually are better after posterior compared with anterior infarcts of enzymatically equal size.