INTRODUCTION. Moderate to severe stenosis is the less prevalent among the forms of carotid atherosclerotic disease), but it carries a high risk of ischaemic stroke. AIM. To characterise factors associated with moderate to severe carotid stenosis in a high-risk population. PATIENTS AND METHODS. We performed an analysis on traditional risk factors associated with carotid stenosis >= 50% in 533 patients who received Doppler ultrasound due to a history of stroke (34%) or who had = 2 of the risk factors: age >= 55 years (86%), hypertension (65%), dyslipidemia (52%), obesity (42%), diabetes (40%) or smoking (40%). RESULTS. The prevalence of carotid stenosis >= 50% was 7.1%, symptomatic (associated with stroke in congruent territory) in 5.6%, bilateral in 2.1% and bilateral symptomatic in 1.5%. A 36.8% of patients had moderate to severe load (>= 4) of atherosclerotic plaques (25.9% moderate: 4-6 plaques, and 10.9% severe: >= 7 plaques). By multivariate analysis we identified the age >= 75 years, dyslipidemia, and smoking as factors independently associated with carotid stenosis >= 50%, and hypertension and smoking with symptomatic stenosis. The number of risk factors was strongly associated with the prevalence of carotid stenosis. Notably, neither diabetes nor obesity explained the degree of moderate to severe carotid stenosis. CONCLUSIONS. As forms of carotid atherosclerotic disease, moderate to severe stenosis is less frequent than a high burden of atherosclerotic plaques. Advanced age, smoking, dyslipidemia and hypertension are the main traditional risk factors associated with the degree of carotid stenosis.