Twelve patients with a clinical diagnosis of right ventricular infarction are described. All had acute inferior wall myocardial infarction associated with the bedside findings of jugular venous distension, clear lungs on auscultation, and arterial hypotension. Hemodynamically, there was elevation of right-sided filling pressures not explained by normal or minimally elevated pulmonary wedge pressures. Four patients had an incorrect diagnosis of acute cardiac tamponade. However, a review of the data showed that the hemodynamic features of right ventricular infarction more closely resemble those of pericardial constriction, a point that may be helpful in distinguishing right ventricular infarction from cardiac tamponade. Invasive and noninvasive techniques that exclude the presence of pericardial fluid and suggest enlargement and abnormal contractility of the right ventricle were helpful in establishing the diagnosis of right ventricular infarction in several patients.