Decreased low-density lipoprotein (LDL) particle size is associated with coronary heart disease (CHD) risk among middle-aged Caucasian populations, and has been consistently correlated with increased plasma levels of triglyceride and decreased levels of high-density lipoprotein (HDL) cholesterol. This study examines whether these risk factors predict CHD among older Japanese-American men. With use of the Honolulu Heart Program Lipoprotein Exam 3 (1980 to 1982) as baseline, and 12-year follow-up for CHD events, a nested, case-control study was designed. One hundred forty-five incident CHD cases were identified and matched to 2 controls each. LDL particle diameter (size) was determined by gradient gel electrophoresis. A 10-angstrom (Å) decrease in LDL size at baseline was associated with increased risk of incident CHD (relative risk 1.28, 95% confidence interval 1.01 to 1.63). After adjustment for baseline risk factors, the LDL size association was no longer statistically significant (relative risk 1.13, 95% confidence interval 0.86 to 1.49). When principal components analysis was used to define a composite variable for LDL size, triglycerides, and HDL cholesterol, this component predicted CHD independent of smoking, alcohol consumption, physical activity, body mass index, hypertension, diabetes, and β-blocker use (p <0.01). Therefore, this prospective analysis of data from older, Japanese-American men demonstrated that decreased LDL size is a univariate predictor of incident CHD, and that a composite risk factor of LDL size, triglyceride, and HDL cholesterol was a risk factor for CHD independent of other risk factors.