The objective of this prospective observational study was to establish the prevalence of carotid atherosclerosis in an asymptomatic diabetic population and to determine predictive factors for a screening optimization. A total of 300 consecutive type-2 diabetic subjects (166 males, 134 females) underwent a physical examination and duplex carotid scanning. Patients with a recent cerebrovascular event (< or = 6 weeks) or previous carotid surgery were excluded. The prevalence of carotid stenosis > or = 60% or occlusion was 4.7%; the prevalence of carotid atherosclerosis was 68.3%. Risk factors for stenosis > or = 60% or occlusion were the presence of diabetic retinopathy (OR: 3.62; 95% CI: 1.12-11.73), ankle-brachial index (ABI) <0.85 (OR: 3.94; 95% CI: 1.21-12.84) and a personal history of neurological disorders (OR: 4.54; 95% CI: 1.16-17.81). Being female was a protective factor (OR: 0.09; 95% CI: 0.01-0.78). The two factors in the analysis limited to the male population were an ABI < 0.85 (OR: 3.66; 95% CI: 1.04-12.84) and a personal history of coronary heart disease (OR: 3.34; 95% CI: 1.01-11.01). If male diabetics without either of these two factors are excluded, the negative predictive value for carotid stenosis is 96.6%. In conclusion, the prevalence of atherosclerotic carotid disease in diabetic patients is high. In these patients, the probability of finding >60% stenosis is highest among men with a history of coronary heart disease or an ABI <0.85.