In an anatomical study of 187 patients who had died from various heart disorders, the anterior descending artery (ADA) had an intra-mural course in 33 cases (17.65 p. 100). This abnormal course had had no correlation with the sex of the patients, the nature of the disease, length of the trunk of the left coronary artery, and to the relative sizes of the coronary vascular supply on the right and the left. It is associated, to a degree which may reach statistical significance, with certain abnormalities of distrubution of the ADA itself, of other pericardial arteries, and with a particularly short course which means that it does not reach the apex of the heart in more than a third of cases. The anatomical position of the intraparietal segment appears to be remarkably constant, and several anatomical landmarks (the origin of the second anterior septal artery and of the second diagonal artery, both collaterals of the anterior descending artery) may lead one to suspect the presence of an anomaly in the course of the artery when the coronary arteriogram is doubtful. The thickness of the muscular bridge is variable, but is not as a rule great. The most constant anatomical finding is that the anterior descending artery, in its intra-parietal segment, maintains a thin wall, and is never the seat of atheromatous deposits, whatever the age of the patient.