Fever is common in surgical patients. The list of potential causes is long and includes many noninfective etiologies.Only about 40% of fever episodes in hospitalized patients are caused by infection. Any fever in a surgical patient is a cause for concern. New or continuing fever more than three days after surgery should raise a strong suspicion of persistent illness or a new complication. On rare occasions, these fevers can be attributed to potentially life-threatening occult infections, including acute cholecystitis, antibiotic-related pseudomembranous colitis, systemic candidiasis, or transfusion-related cytomegalovirus disease. A change in the microbiology of postoperative infections has also been noticed, characterized by a greater incidence of infections caused by methicillin-resistant Staphylococcus aureus, by polymicrobial flora, and by fungi.Control of nosocomial infections has become more challenging recently because of widespread bacterial resistance to antibiotics and to more frequent surgical indications in elderly patients at higher risk. Early recognition and appropriate treatment of these infections relieves anxiety, reduces hospital costs, and increases patient survival rates.The workup and therapy for the individual patient may differ, depending on the underlying disease and clinical appearance and the clinician's suspicion for infection. Subsequent testing should be based on the clinical findings. Perhaps more money is wasted in the evaluation of early postoperative fever than on any other aspect of postoperative care.