Radionuclide angiographic studies were performed in 26 patients with a first myocardial infarction, 11 with anterior and 15 with an inferior location. Right ventricular (RV) and left ventricular (LV) ejection fractions (EF) were determined. Mean LVEF in anterior infarctions (33.2 +/- 7.3) was lower than in inferior myocardial infarctions (59.9 +/- 10.2) (p less than 0.001). Mean RVEF in the anterior infarct group was 41.3 +/- 15.1 and in the inferior myocardial infarction group 33.7 +/- 12.8 (p = NS). RVEF was less than 40% in 11 of 15 (73%) with inferior and 7 of 11 (66%) with anterior myocardial infarction. The ratio of LVEF:RVEF was 0.84 +/- 0.19 in the anterior and 2.13 +/- 1.28 in the inferior myocardial infarction group (p less than 0.001). LVEF correlated with RVEF in patients with anterior infarcts (r = 0.77; p less than 0.05) but not in those with inferior myocardial infarction (r = 0.14). RV regional wall motion abnormalities were observed in the inferolateral zones in 10 of 15 (66%) with inferior and in none of the 11 patients with anterior myocardial infarctions (p less than 0.001). Inferoseptal wall motion abnormalities were observed in 3 of 15 (20%) with inferior and 6 of 11 (56%) with anterior myocardial infarctions (p = NS). RV dysfunction in the inferior infarctions is probably an expression of primary RV dysfunction rather than secondary to LV dysfunction. RV dysfunction was proportional to LV dysfunction in the anterior infarction group and was often accompanied by RV septal contraction abnormalities.