BACKGROUND AND OBJECTIVES: The goals of this study were to investigate the prevalence and risk factors of carotid atherosclerotic stenosis and also the predictors for the progression of carotid atheroslcerotic stenosis in Korean adults. SUBJECTS AND METHODS: Carotid ultrasonography was performed for 22,782 adults who volunteered for a routine health check-up. Carotid atheroslcerotic stenosis was defined as a finding of at least one lesion of an intima-media thickness greater than 1.2 mm with atherosclerotic plaque. Among the 22,782 people, 4,077 persons underwent follow-up carotid ultrasonography at an average interval of 27.6 months. The past medical history and information on the cardiovascular risk factors were obtained from standardized questionnaires and the subjects' blood chemistry. RESULTS: Carotid atheroslcerotic stenosis was detected in 1,875 adults (8.2%) and it was significantly associated with a history of stroke, hypertension, heart disease, hyperlipidemia, higher HbA1C, older age, a wider pulse pressure, lower HDL-cholesterol and a large amount of smoking (p<0.05). In the subjects without history of stroke (22,444 persons), those with more than 5 risk factors showed a higher prevalence (36.8%) of carotid atherosclerotic stenosis than those with a history of stroke (29.0%). The independent predictors of stenosis progression were older age, male gender, hypertension, a large amount of smoking, a high LDL cholesterol level, a low HDL-cholesterol level and a high fibrinogen level (p<0.05). CONCLUSION: Carotid ultrasonographic screening for a population with these risk factors will lead to a more efficient screening process and our identification of the predictors of disease progression may help to design therapeutic trials for preventing the progression of carotid atherosclerotic stenosis.