Platelets may contribute to the pathogenesis of atherosclerosis and to the complications of coronary atherosclerosis, acute myocardial infarction, unstable angina, and sudden cardiac death. In addition, platelets may contribute to saphenous vein aortocoronary graft occlusion. Of 104 men with coronary artery disease, platelet survival (SURV) (chromium51 labeling) was shortened in 68% (3.1+/-0.03 days [average+/-SEM]; normal, 3.7+/-0.03 days; P greater than .001). Three platelet-suppressant drugs, sulfinpyrazone, clofibrate, and dipyridamole increased SURV. Saphenous vein graft occlusion was associated with shortened SURV. Of 36 men with occlusion of at least one graft, SURV was shortened in 35 (2.5+/-0.08 days), whereas in 19 with all grafts open, SURV was shortened in six (3.5+/-0.10 days; P less than .01). These drugs increased SURV (2.3 +/- 0.08 to 2.7 +/- 0.11 days; P less than 0.1) and were associated with improved graft patency (four of 32 grafts after initial bypass vs 30 of 34 grafts open after second operation).