In a series of 75 patients with transmural acute myocardial infarction, a right to left ventricular filling pressure ratio equal to or greater than 0.65 was assumed to be indicative of associated right ventricular infarction. Eleven (24%) out of 45 patients with infero-posterior myocardial infarction had such hemodynamic evidence of right ventricular infarction (Group A). The remaining 34 patients with infero-posterior myocardial infarction (Group B) and the 30 patients with anterior myocardial infarction did not. Two-dimentional echocardiographic examination performed 5 days after admission in the 62 patients who survived, showed right ventricular free wall asynergy in six out of eight Group A patients: in three of them right ventricular enlargement was present. No patient in Group B inferior infarction or with anterior myocardial infarction had abnormal right ventricular motion or dimensions.