Type 2 diabetes is characterized by increased plasma triglyceride levels and a fourfold increase in ischemic heart disease, but the mechanism is unclear. CD36 is a receptor/transporter that binds fatty acids of lipoproteins. CD36 deficiency has been linked with insulin resistance. There is strong evidence of in vivo interaction between platelets and atherogenic lipoproteins suggesting that atherogenic triglyceride-rich lipoproteins, such as VLDL, that are increased in diabetic dyslipidemia are important in this process. This study demonstrates that VLDL binds to the platelet receptor CD36, enhances platelet thromboxane A2 production, and causes increased collagen-mediated platelet aggregation. VLDL enhanced collagen-induced platelet aggregation by 1) shortening the time taken for aggregation to begin (lag time) to 70% of control (P ؍ 0.001); 2) increasing maximum aggregation to 170% of control (P ؍ 0.008); and 3) increasing thromboxane production to 3,318% of control (P ؍ 0.004), where control represents platelets stimulated with collagen (100%). A monoclonal antibody against CD36 attenuated VLDLenhanced collagen-induced platelet aggregation by 1) inhibiting binding of VLDL to platelets by 75% (P ؍ 0.041); 2) lengthening lag time to 190% (P < 0.001); and 3) decreasing thromboxane production to 8% of control (P < 0.001). In support of this finding, platelets from Cd36-deficient rats showed no increase in aggregation, thromboxane production, and VLDL binding in contrast to platelets from rats expressing CD36. These data suggest that platelet Cd36 has a key role in VLDLinduced collagen-mediated platelet aggregation, possibly contributing to atherothrombosis associated with increased VLDL levels. Diabetes 52:1248 -1255, 2003 I ndividuals with type 2 diabetes have at least four times greater risk of developing ischemic heart disease (IHD) than the general population. Type 2 diabetes and the metabolic syndrome are also associated with the atherogenic lipoprotein phenotype (1), characterized by elevated plasma triglyceride, increased VLDL production, increased small dense LDL levels, as well as decreased HDL. Recent data provide convincing evidence that increased plasma triglyceride levels are an independent risk factor for IHD (2), but the mechanism linking increased plasma triglyceride-rich lipoproteins, such as VLDL, to IHD remains uncertain.Type 2 diabetes is associated with increased plasma markers of platelet activation (3-5), and pharmacological intervention to reduce plasma triglycerides results in reduction in markers of platelet activation (6). Platelet activation plays an integral role in atherothrombosis (7), since platelet aggregation forms the scaffolding for the initiation of a platelet plug after damage to the vascular wall or rupture of atherosclerotic plaque. It is increasingly apparent that atherogenic lipoproteins and platelets interact both in vivo and in vitro, producing a procoagulant phenotype (8 -11), but the molecular interaction between triglycerides and platelets has not been elucida...