PURPOSE: To determine the prevalence and degree of CAC (coronary artery calcification) in appearently healthy middle-aged Koreans, and the relation of CAC to risk factors for atherosclerosis. MATERIALS AND METHODS: A total of 289 apparently healthy personnel at Yonsei University (male: 170, female: 119, age: mean(SD=54.9 +/-7.1 years) underwent EBT (electron bean tomography). The risk factors for atherosclerosis, which included diabetes mellitus, hypertension, smoking, a family history of precocious onset, obesity, hyperlipidemia, and high intraperitoneal fat, were scrutinized. One hundred and sixty-eight subjects (58 % ) had at least one risk factor. The CAC score was calculated for all subjects and for each coronary artery separately and was then analyzed by age and sex and in relation to the risk factors. RESULTS: The prevalence of CAC was 40% in men and 18.5% in women (mean score: 29.7 vs. 9.9). The number of individuals who had one, two, or more than two risk factors was 141, 41, and 19, respectively. The number of risk factors and the prevalence and score of CAC were significantly correlated (p=0.01, 0.02 respectively). The number of individuals with no risk factor, with without CAC, was 58(20.1%) and 103(35.6% ) , respectively, while the number with some risk factor, with or without CAC, was 38(13.1%) and 90(31.1%), respectively. The CAC score was significantly higher in the presence of hypertension, low HDL, or obesity (p=0.001, 0.049, and 0.068, respectively). Smoking appeared to have a borderline effect on the calcium score (p=0.118). CONCLUSION: This study should provide useful information for interpreting CAC scores and establishing a treatment strategy for Koreans. The comparison of our results with other studies will enable a better understanding of the process and risk factors of atherosclerosis in Koreans.