We investigated the prevalence of carotid atherosclerosis, including mild early lesions, and its association with cervical bruits and various risk factors (age, male sex, hypertension, hyperlipidemia, diabetes mellitus, obesity, and cigarette smoking) in 232 consecutive Japanese patients. High-resolution real-time B-mode ultrasonography was performed to determine the extent of atherosclerosis, and it was quantified by using a scoring system. The prevalence of carotid atherosclerosis was 49%, 59%, and 41% in all 232 patients, the 100 symptomatic patients, and the 132 asymptomatic patients, respectively. Although carotid lesions were detected frequently (87%) in the 30 patients with cervical bruits, bruits were noted in only 30% of the 88 examined patients with carotid atherosclerosis. Independent risk factors for carotid atherosclerosis in these patients were found to be age, male sex, and hyperlipidemia; diabetes mellitus was a possible risk factor for carotid atherosclerosis. Our study did not show a close association between hypertension and carotid atherosclerosis, and this might be caused by the high prevalence of hypertension in our patients. Our findings suggest an increasing prevalence of carotid atherosclerosis in the Japanese, though this should be confirmed in a population-based study. Our study demonstrates the clinical usefulness of high-resolution B-mode ultrasonography for the evaluation of early carotid atherosclerosis.