Publisher Summary This chapter discusses the arterial embolism. Arterial emboli that originate within the heart are 90%. Within the left ventrical, thrombus forms most commonly as a sequel to myocardial infarction. The homeostatic balance between the thrombosis and thrombolysis in the area of ischaemic endocardium is probably disturbed in favor of thrombogenesis by the release of platelet activating esterases and amines such as adenosine diphosphate and 5-hydroxytryptamine from dying cells, and impairment of fibrinolytic systems may take place. Acute embolic occlusion of an artery adversely affects the limb or organ rendered ischaemic and equally significant, the artery itself, in addition to producing generalized systemic effects in the patients. The extent of local ischaemia and its clinical relevance depends upon several factors including the level of occlusion within the arterial tree, the length of artery involved, and the extent of existing collateral pathways. In pathological terms the immediate effect of the acute arterial occlusion may be related to the loss of function of the affected limb or organ.