The classic clinical picture of an arterial embolism is that of a dual series of events consisting of (1) a sudden arterial occlusion, and (2) a thrombogenic cardiopathy. The diagnostic equation of an arterial embolism would appear, therefore, to be extremely simple. A reevaluation of the problem, however, based on 25 years of personal experience, while it showed that the majority of cases may fit the classic description, also disclosed a number of unusual diagnostic and surgical aspects still not widely recognized. Special diagnostic problems are primarily concerned with the occurrence of emboli in patients without an apparent source of thrombosis, incompleteness of arterial occlusion, multiple arterial emboli to the same extremity, and embolic occlusion superimposed on arteriosclerosis obliterans. Special therapeutic problems are primarily concerned with late embolectomy, repeated embolectomy, and some aspects referable to embolism associated with mitral surgery and long-term anticoagulation. The statistical significance of the foregoing clinical