A 14-year old asymptomatic boy was diagnosed as having a large calcified subaortic left ventricular aneurysm that was found to obstruct flow across the right pulmonary artery during systole. Surgical patch closure of the neck of the aneurysm resulted in relief of obstruction. The case is reported for its rarity, massive calcification, absence of aortic regurgitation and dynamic compression of the right pulmonary artery.