Surgical patients have a high risk of infections. In the breast surgery, a "clean" surgery, the infection rate should not be more than 2%. In this work, we have studied 174 women with breast cancer, which did not receive the antibiotic prophylaxis. After surgery the patients were monitored for infective complications. The total incidence of infections was 5.1%: 3.4% of surgical wound infections and 1.7% of nosocomial infections. The preoperative antibiotic therapy should not be used in the "clean" surgery, as the mastectomy, except in the patients with high infective risk. In fact we can prevent the wound infections of breast surgery with adequate control measures about the aseptic procedures of operating suite, the members of the surgical team and the preparation of the patient.