In an analysis of 236 consecutive patients with acute limb ischemia treated as embolic event, using only the Fogarty catheter, 30 cases of arterial thrombosis were identified. This group was compared with 92 patients with true embolism. Surgical failure was significantly more common in the thrombosis than in the embolism group (50% vs. 13%). The rate of hospital deaths was high (27%) among the patients with thrombosis, and there was close correlation (r = +0.76) between early postoperative gangrene and early death in these patients, but not in those with embolism. Severe ischemia, advanced age and surgical failure were significant risk factors for mortality in the patients with thrombosis. The authors conclude that early identification of these patients is important, that risk factors should be evaluated and that operations should be done by surgeons accustomed to procedures for adequate revascularization, since simple thrombectomy is associated with high rates of failure and mortality.