The number of clinical, pathologic and experimental observations published on coronary occlusion, its effect and its recognition attest the interest that exists in the subject and its importance as a clinical problem. The very multiplicity of these observations gives rise to the need for their critical evaluation and integration. It is the purpose of this article to make such an integration. ANATOMIC CONSIDERATIONS The first requisite to an understanding of the problem of coronary occlusion is a certain fundamental knowledge of the anatomy of the coronary arteries in the heart of man. The work of Whitten,1Gross2and Spalteholz3on the coronary circulation covers the subject exhaustively. The anterior descending branch of the left coronary artery supplies the anterior portion of the left ventricle and apex and the anterior two thirds of the interventricular septum and gives off a few branches to supply a narrow zone of