The purpose of this study was to identify predictors of atherosclerosis in a healthy young cohort comprised of 241 subjects who underwent a regular employee medical check-up at Ohshima National Sanatorium over a 9-month period. All subjects underwent carotid ultrasound examinations to determine maximal common carotid artery intima media thickness. In addition, serum total cholesterol, triglycerides, high-density lipoprotein cholesterol, blood urea nitrogen, creatinine, glucose, and insulin were evaluated. The subjects were relatively young (mean age, 44 years; range, 18 to 62 years), with 130 females (54%) and 111 males (46%). Maximal common carotid artery intima media thickness was predicted by smoking habit, body mass index, fasting blood sugar, fasting serum insulin, and systolic blood pressure (F(5,235) = 52.8, P < 10(-5)). There was clear separation in common carotid artery intima media thickness values based on body mass index, smoking, and fasting serum insulin, and somewhat more overlap with systolic blood pressure and fasting blood sugar. These findings suggest that smoking and high values of body mass index, fasting serum insulin, systolic blood pressure, and fasting blood sugar are warning factors for early atherosclerosis development, and could conceivably serve as the basis of diagnostic screening. Smoking is particularly deleterious, as smokers with high body mass index, high fasting serum insulin, or high systolic blood pressure tend to have larger common carotid artery intima media thickness values than would have been predicted by consideration solely of the individual risk factors.