We have studied the localization of early sudanophilic and fibrous plaques in the main stem and proximal branches of opened and stained left coronary arteries. The distribution of lesions was separately assessed by a computer technique. The early sudanophilic lesions develop in the proximal portion of the coronary artery branches and subsequent lesions spread distally and appear first and most prominently in the left anterior descending branch. Around the bifurcation both sudanophilic and fibrous plaques had a distinct spatial distribution with peak incidence on the outer walls. In contrast, the flow divider and the inner walls downstream from it were relatively free of disease.