A 68-year-old man with known coronary heart disease experienced rapidly progressive cardiac dysfunction and was found to have occult cardiac amyloidosis at autopsy. The amyloidosis was undiagnosed during life and initially at autopsy. Marked diffuse involvement of the intramural coronary arteries by amyloid deposits resulted in severe luminal compromise of numerous medium and small vessels. The myocardium proper was virtually spared from amyloid deposits. Amyloid-related coronary narrowing contributed to cardiac ischemia and sudden death. The significance of amyloid coronary disease in this patient relates primarily to the difficulty in considering the diagnosis when other reasons for cardiac signs and symptoms preexist. Also, the adverse effects of amyloid coronary disease may be profound without direct myocardial involvement.