BACKGROUND Although a greater than normal intima-media thickness (IMT) has been found in older coronary patients, the data for younger patients are lacking. OBJECTIVE To determine the carotid IMT in patients with premature myocardial infarction. METHODS We measured IMT (common and internal carotid, carotid bifurcation) in 30 coronary patients, aged 30-50 years (mean 46 years), who had survived myocardial infarctions 1-9 years (mean 6 years) earlier, and in 30 age-matched men without clinically evident coronary heart disease (controls) by B-mode ultrasonography. Blood levels of lipoproteins, glucose, iron and transferrin, fibrinogen, tissue plasminogen activator (t-PA) antigen level and activity and plasminogen activator inhibitor (PAI-1) antigen level and activity were also determined. RESULTS IMT in all segments of carotid arteries in the patients was significantly greater than that in the controls (P < 0.0001). The presence of atherosclerotic plaques was correlated to greater than normal carotid IMT. Other risk factors displaying statistically significant correlations to mean carotid IMT were t-PA antigen level and activity, PAI-1 antigen level and level of high-density lipoprotein cholesterol. CONCLUSIONS The significant association between carotid IMT and coronary heart disease suggests that carotid and coronary atherosclerosis evolve simultaneously. Hence carotid IMT can be used as a predictor of coronary atherosclerosis.