Obstruction of Starr-Edwards tricuspid prostheses occurred in seven patients from 2 to 52 months after surgery. Four patients were taking anticoagulants. Three patients presented with acute right-heart failure, three were asymptomatic, and one died suddenly. Of the six who were examined, all had high-pitched tricuspid diastolic murmurs and elevated jugular venous pressure, five had hepatomegaly, and three had peripheral edema. Cardiac catheterization in four patients revealed elevated right atrial pressure in all and large transvalvular pressure gradients in three. Angiography showed impaired flow across the valve in all cases. In six cases, impingement of a prosthesis strut on the ventricular myocardium was the underlying mechanism of obstruction. Two patients died without reoperation. Four of the remaining five patients survived reoperation and were improved. Tricuspid ball-valve obstruction is a potentially lethal complication that may develop with minimal symptoms. A characteristic diastolic murmur and elevated systemic venous pressure have uniformly been present. Confirmatory hemodynamic studies should be followed by early reoperation.