This study was performed to determine whether postprandial hypertriglyceridemia can affect the endothelial function. Endothelial function was assessed by flow-mediated endothelium-dependent brachial artery vasodilation (FMD) which was defined as percentile changes of diameter. Thirty one patients were enrolled in this study. The serum lipid profiles and FMD were measured at fasting, and after low fat and high fat meals. The serum triglycerides at 2 hours after a high fat meal were significantly increased compared to those measured at 2 hours after a low-fat meal and at fasting state (P<0.05). The FMD was transiently decreased (P<0.0001) from $11.4{pm}3.2\%$ at fasting state to $6.5{pm}2.5\%$ after a high-fat meal. The FMD was inversely related with postprandial hypertriglyceridemia (P<0.05). In conclusion, this study may suggest that postprandial hypertriglyceridemia causes endothelial dysfunction.