The importance of postoperative wound infection in major amputations was elucidated by recording the organisms isolated in preoperatively infected gangrene and in postoperatively infected wounds of patients undergoing lower-limb amputations for ischemia. Sixty-four amputations were performed on 61 patients. The frequency of coexisting diabetes mellitus was 34%. Postoperative infections occurred in nearly two-thirds of the 19 cases of infected gangrene, as compared with less than one-third of cases of noninfected gangrene. The presence of diabetes mellitus did not significantly influence the infection rate. Preoperatively as well as postoperatively, the most frequently isolated bacterium was Staphylococcus aureus. Clostridium perfringens was cultured in four cases. Postoperative wound infection following lower-limb amputation for ischemia is the main reason for reamputation, especially in patients with infected gangrene.