A study was undertaken to determine the prevalence of asymptomatic atherosclerotic carotid artery bifurcation disease in patients presenting with claudication; thus 263 consecutive patients with intermittent claudication, but without recent or old cerebrovascular symptoms were studied by routine carotid duplex scanning. Of the 263 patients, 124 (47.1%) had a C, D, D+ or E lesion in some vessels of the carotid bifurcation and 54 (20.5%) had a D, D+ or E lesion of the common or internal carotid arteries. Women had a higher prevalence of significant carotid stenosis (29.6% v. 18.2% in men) as did patients over the age of 70 years (28.6% v. 16.3% if below 70 years). It is concluded that the prevalence of clinically significant carotid bifurcation disease (greater than 50% stenosis in the common or internal carotid arteries) in patients with claudication is high (20.5%). The presence of an asymptomatic high-grade stenosis (D+ or E) in 11.8% of patients with claudication should alert the clinician that he is treating a patient who is at a high risk of developing cerebrovascular ischaemic complications.