Acute limb ischemia is one of the most potentially devastating but treatable diseases faced by the vascular surgeon. It is crucial to identify the ischemic process early, as the outcomes of early intervention can lead to limb salvage, whereas late recognition places the patient at risk for limb loss and potential mortality. This article emphasizes the importance of properly evaluating the acutely ischemic extremity to ascertain whether the etiology is embolic or thrombotic. Appropriate treatment and management of the limb are determined by the underlying cause of the ischemia. The authors will review the clinical features, angiographic findings, and strategies for management for these similar but distinct etiologies: acute embolic versus thrombotic limb ischemia.