Infectious diseases account for one third of all deaths in people 65 years and older. Early detection is more difficult in the elderly because the typical signs and symptoms, such as fever and leukocytosis, are frequently absent. A change in mental status or decline in function may be the only presenting problem in an older patient with an infection. An estimated 90 percent of deaths resulting from pneumonia occur in people 65 years and older. Mortality resulting from influenza also occurs primarily in the elderly. Urinary tract infections are the most common cause of bacteremia in older adults. Asymptomatic bacteriuria occurs frequently in the elderly; however, antibiotic treatment does not appear to be efficacious. The recent rise of antibiotic-resistant bacteria (e.g., methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococcus) is a particular problem in the elderly because they are exposed to infections at higher rates in hospital and institutional settings. Treatment of colonization and active infection is problematic; strict adherence to hygiene practices is necessary to prevent the spread of resistant organisms. (Am Fam Physician 2001;63:257–68.)