As ultrasonographically assessed carotid arteriosclerosis is being used as a surrogate measure for coronary arteriosclerosis, we performed a prospective longitudinal study of the association of our high-resolution ultrasound assessment of extracranial carotid morphology with the risk of acute coronary events in 1,288 eastern Finnish men. The presence of any structural changes in the common carotid arteries or carotid bulbs was associated with a 3.29-fold (95% confidence interval, 1.31-8.29; p = 0.0074), intimal-medial thickening with a 2.17-fold (95% confidence interval, 0.70-6.74; p = NS), small carotid plaques with a 4.15-fold (95% confidence interval, 1.51-11.47; p less than 0.01), and large ("stenotic") plaques with a 6.71-fold (95% confidence interval, 1.33-33.91; p less than 0.01) risk of acute myocardial infarction compared with men free of any structural changes in the carotid artery wall at baseline. These data confirm the close relation between carotid artery wall morphology and coronary heart disease.