The incidence of postoperative infections, especially due to multi-drug resistant strains such as Pseudomonas sp., Enterococcus sp., and Methicillin resistant Staphylococcus aureus (MRSA), is high in compromised hosts. Among them, respiratory infection, catheter sepsis, and drug-associated enteritis are frequently observed and respiratory infection is liable to fall into serious illness. These infections have characteristics in causative organisms. Pseudomonas aeruginosa or MRSA are frequently isolated in respiratory infections and Candida or coagulase-negative staphylococcus are frequently isolated in catheter sepsis. G-test in addition to blood culture is necessary for early diagnosis of Candida sepsis, vancomycin should be administered in early phase of antibiotic-associated enteritis, since this infection is usually caused by MRSA or Clostridium difficile and frequently falls into serious illness. The patients with protein-calorie malnutrition, liver cirrhosis, renal failure, diabetes melitis, administration of anticancer drugs and/or radiation therapy, serious injury, or severe operative stress are considered to be compromised hosts in surgical field, and the adequate perioperative managements according to these disorders should be carried out against postoperative infections.