Two patients with extensive anterior myocardial infarction developed a hitherto unreported type of right ventricular outflow tract obstruction. A 71-year-old woman, who had had an acute infarction 10 years before, was admitted for sustained ventricular tachycardia. A loud ejection murmur was heard in the mid-precordium. The echocardiogram and left ventriculogram showed a septal aneurysm, with a systolic gradient of 21 mmHg between the right ventricular outflow tract and apex. The ejection murmur was detected in the outflow tract by intracardiac phonocardiography. The second patient was a 60-year-old man who had had an acute infarction at age 47. He was also referred because of ventricular tachycardia, and his clinical situation was almost the same as that of the first case. Our search of the literature failed to disclose any similar case with a loud ejection murmur confirmed by intracardiac phonocardiography to be due to an obstructive septal aneurysm.