BACKGROUND Atherosclerotic occlusion of a coronary vessel is the commonest cause of ischaemic heart disease. The distribution of atherosclerotic lesions is not random,with stenoses preferentially situated at branch ostia, bifurcation points, and the proximal segments of daughter vessels. The aim of this study was to determine the effect of the intrinsic anatomical properties of the left main coronary artery(LMCA) on the distribution of atherosclerotic lesions in its branches. METHODS A retrospective review of 170 consecutive coronary angiograms obtained from the cardiac catheterisation laboratories of private hospitals in the eThekwini Municipality area of KwaZulu-Natal, South Africa was performed. The LMCA was absent in 19/170 (11.2%). The remaining angiograms(n = 151) were divided into two groups: normal 63/151 (41.7%) and those with coronary artery disease (CAD) 88/151 (58.3%). The CAD group was sub-divided into proximal 42/88 (47.7%), mixed (proximal and distal) 26/88 (29.6%) and distal20/88 (22.7%) sub-groups based on the location of atherosclerotic lesions in the branches of the LMCA. CONCLUSIONS The mean length, diameter and angle of division of the LMCA were as follows: Total angiograms: 10.4 mm, 3.8 mm and 86.2o; normal group:10.5 mm, 3.9 mm and 85.7o, CAD group: 10.2 mm, 3.7 mm and 86.3o; proximal sub-group: 10.9 mm, 3.7 mm and 91.6o, mixed sub-group - 9.8 mm, 3.7 mm and 85o and distal sub-group - 9.1 mm, 3.8 mm and 79.4o, respectively. The vessels with proximally located lesions were recorded to have longer lengths and wider angles of division than vessels with distal lesions. Coronary angiographic delineation of the LMCA anatomy may be predictive of a coronary arterial arrangement that may favour the progression of proximally located lesions.