A case is presented of fatal coronary embolism of Teflon felt used to buttress sutures in the placement of a Björk-Shiley aortic valve prosthesis. The embolism occurred on the tenth postoperative day, lodging in the left anterior descending branch of the left coronary artery 5.5 cm. from the ostium, causing a large anterior myocardial infarct. The patient died in less than 24 hours following the infarct. A review of the literature indicates that this is the first reported case of clinically significant embolism of Teflon felt used in the placement of a Björk-Shiley aortic valve.