With the general aging of the United States population we can expect to encounter increasing numbers of elderly patients with surgical infections. To further delineate this population, patient attributes, treatment characteristics, and outcomes were examined in elderly patients with surgical infection. All infections from December 1996 through May 2000 occurring on the inpatient, adult general, and trauma surgical services at a university hospital were studied prospectively. Characteristics, comorbidities, and outcomes were examined in patients > or = 70 years of age and compared with those of patients <70 years of age. Elderly patients had significantly higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores (15.4 +/- 0.3 vs 11.2 +/- 0.2, P < 0.001) and greater numbers of comorbidities than the younger population. The Acute Physiology score; infecting organisms; and rates of pneumonia and intra-abdominal, central line, and bloodstream infection were similar between groups. Crude mortality (21.7% vs 8.1%, P < 0.001) and mortality associated with pneumonia (31.0% vs 17.2%, P = 0.005), central venous catheter infection (50.0% vs 17.4%, P < 0.001), bloodstream infection (32.3% vs 16.6%, P = 0.006), and intra-abdominal infection (23.2% vs 6.3%, P < 0.001) were significantly higher in the elderly. Logistic regression analysis identified APACHE II score, cerebrovascular disease, and fungal infection as independent predictors of mortality in the elderly population. Surgical infection in the elderly is associated with a high mortality and requires special consideration when treating this unique population.