This study reports the results of routine evaluation to detect coronary and carotid atherosclerosis in 200 asymptomatic and hypercholesterolemic patients (48 +/- 10 years: 72.5% men). All patients underwent physical examination, blood lipid profile, an exercise test and cervical echo-doppler. If the exercise electrocardiogram was abnormal, a thallium isotope scan and/or coronary arteriography were performed. Hypercholesterolemia was severe (3.03 +/- 0.52 g/l). 77.5% of patients had pure hypercholesterolemia. Carotid atherosclerosis in the form of plaque (27.5%) or stenosis (3.5%) was found in 31% of patients. This carotid atheroma was commoner in older patients (51.9 +/- 9 years as against 47 +/- 10 years, p < 0.01). Twenty patients (10%) had electrical signs of ischemia provoked by exercise. Six of them had a normal thallium isotope scan and did not undergo coronary arteriography. Coronary arteriography was abnormal in 10 patients (5%): 7 had stenotic lesions and 3 showed evidence of spasm during the methylergometrine test. In total, the hypercholesterolemic patients investigated here were characterised by subclinical atherosclerosis which was frequent but certainly underestimated by non-invasive studies. The existence of an atherosclerotic lesion is an additional argument in favour of starting cholesterol-lowering treatment.