The values of several non-invasive methods for the diagnosis of right ventricular necrosis in inferior myocardial infarction were compared in 51 consecutive patients who underwent serial radionuclide ventriculography, pyrophosphate scintigraphy, and cross sectional echocardiography. In addition a unipolar electrocardiographic lead V4R was recorded on admission, daily, and during episodes of further pain. Profound right ventricular dysfunction was evident in 50% of patients studied by radionuclide methods after inferior myocardial infarction but recognition on clinical groups alone was poor. Functionally important right ventricular infarction was best detected and followed serially by radionuclide ventriculography. Echocardiographic methods for evaluating right ventricular ejection fraction correlated poorly with radionuclide methods. Increased uptake of radioactivity by the right ventricle on pyrophosphate scintigraphy usually indicated poor right ventricular function, but a scan that was negative in the right ventricular territory did not exclude dysfunction. ST segment elevation in V4R was not specific for right ventricular infarction and its routine use may lead to overdiagnosis of this condition. Serial measurements suggest that profound right ventricular dysfunction persists after acute inferior infarction and is associated with considerable morbidity and mortality. Of 25 patients with severe right ventricular dysfunction, six died in the late hospital period. In the remaining 19 patients mean right ventricular ejection fraction over a two month period did not improve; six patients had persistent right ventricular dyskinesia and features of chronic right ventricular failure developed in three survivors.