From December 1990 to July 1995 we performed 171 sub-inguinal revascularizations including 35 popliteal revascularizations and 146 revascularizations of an artery in the leg or foot. Five cases of infection were observed within a delay of 7 and 25 days after the operation. There were 3 men and 2 women (mean age 78 years). Four femoro-tibial bypasses were made for critical ischaemia (2 necroses of the toes, one eschar of the heal, one stage III). There was one femoro-popliteal bypass which was associated with a femoro-femoral for necrosis of the toes. Two bypasses were made with polytetrafluoroethylene, one with Dacron and two with the greater saphenous vein. Signs of sepsis were bleeding in 2 patients who had a venous bypass and septicaemia in 2 patients. Local skin necrosis and/or apparently infected discharge or patent pus were seen in all patients. Staphylococcus aureus was found in 4 patients and Enterobacter cloacae in one. Revascularization was done with an extra-anatomic bypass in 4 patients and with a cryopreserved in situ allograft in 1. Mortality was 20% and amputation rate was 40%. All exposed bypasses were infected but the severity of the infection varied depending on the causal germ, general signs and ischaemia of the limb. Conservative treatment has its limits: 1) intact anastomoses, 2) absence of bleeding, 3) patent bypass, 4) absence of generalized sepsis. Results of in situ revascularization depend on the virulence of the causal germ. Radical treatment (explanation + extra-anatomic revascularization) still has indications in infected infra-inguinal bypass surgery.