Background: The measurement of low density lipoprotein (LDL) particle size has a possibility of a predictor for atherosclerosis. The aim of this study is to investigate the relationship of LDL particle size to carotid intima-media thickness (IMT), the levels of insulin resistance and oxidative stress in healthy Korean adults. Methods: The subjects were total 99 who were clinically healthy and without medications that might alter glucose and lipid metabolism. Carotid intima-media thickness was measured by high resolution ultrasonography, mean LDL particle size by electrophoresis, insulin resistance by kitt value of short insulin tolerance test, and oxidative stress by MDA (malondialdehyde) absorption levels. Results: Carotid intima-media thickness was not significant correlated with LDL particle size. LDL particle size was significantly correlated with age, waist circumference, male gender, total cholesterol, triglyceride, HDL cholesterol, HbA1c levels, insulin resistance, and oxidative stress by simple Pearson`s correlation, but the independent predictors of LDL particle size determined by multiple stepwise regression analysis were serum triglyceride, HDL cholesterol level, age, kitt, and oxidative stress. Conclusion: In healthy Korean adults, the best predictors for LDL particle size were serum triglyceride level, HDL cholesterol level, age, insulin resistance and oxidative stress. Small dense LDL was not a predictor of IMT.