We investigated (1) the relationship between low-density lipoprotein cholesterol (LDL-C) and vascular function in patients receiving and those not receiving statin therapy and (2) optimal level of LDL-C for maintenance of vascular function. Flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) were inversely correlated with LDL-C in the 957 statin naïve subjects but not in the 392 subjects receiving statin therapy. In statin naïve subjects, non-high LDL-C (≤100 mg/dL) was independently associated with a decrease in adjusted odds ratio of the low tertile of FMD (OR: 0.62, 95% CI: 0.45-0.85; P = 0.003) and NID (OR: 0.69, 95% CI: 0.50-0.96; P = 0.03). Adjusted odds ratio of the low tertile of FMD was significantly lower in the low LDL-C group (≤70 mg/dL) (OR: 0.47, 95% CI, 0.27-0.81; P = 0.006) and in the moderate LDL-C group (70.1-100 mg/dL) (OR: 0.66, 95% CI, 0.48-0.94; P = 0.02) than in the high LDL-C group (>100 mg/dL). There was no significant difference in FMD between the low LDL-C group and moderate LDL-C group. There were significant relationships of FMD and NID with LDL-C levels in statin naïve subjects. In a general population, LDL-C of ≤100 mg/dL may be the optimal target level for maintenance of endothelial function.