The aim of this study was to visualise and analyse the status of the main left coronary artery by 2D echocardiography before coronary angiography. Fifty two patients were studied. The recordings were performed from the left parasternal position on video cassettes and played back frame by frame for each patient, to analyse the left main coronary artery and its bifurcation. The patients had known stenosis of this vessel; there were echocardiographic abnormalities in all 10 cases; the stenosis was visualised directly in 5 patients and the vessel was considered to be abnormal in the other 5 patients. Forty two patients underwent 2D echo before coronary angiography. The echo of the left main coronary artery was considered to be abnormal in 8 patients: these results were compared with those of coronary angiography. In 33 cases there were no echocardiographic abnormalities and there were no angiographic lesions. The false positive results were due to the inability to record the bifurcation (proximal stenosis of the LAD interpreted as stenosis of the left main coronary) or to the direction of the left main coronary which is curved and thus cannot be analysed in the plane of the transducer. False negative results corresponded to slight stenosis (less than 50 p. 100). The bifurcation can be visualised in 60 p. 100 of patients with normal left main coronary arteries. It is only in these cases that the absence of significant lesions can be confirmed before coronary angiography.