Approximately 2 million nosocomial infections occur annually in the United States. These infections result in substantial morbidity, mortality, and cost. The excess duration of hospitalization secondary to nosocomial infections has been estimated to be 1 to 4 days for urinary tract infections, 7 to 8.2 days for surgical site infections, 7 to 21 days for bloodstream infections, and 6.8 to 30 days for pneumonia. The estimated mortalities associated with nosocomial bloodstream infections and pneumonia are 23.8% to 50% and 14.8% to 71% (overall), or 16.3% to 35% and 6.8% to 30% (attributable), respectively. The estimated average costs of these infections are $558 to $593 for each urinary tract infection, $2,734 for each surgical site infection, $3,061 to $40,000 for each bloodstream infection, and $4,947 for each pneumonia. Even minimally effective infection control programs are cost-effective. In countries with prospective payment systems based on diagnosis-related groups, hospitals lose from $583 to $4,886 for each nosocomial infection. As administrators focus on cost containment, increased support should be given to infection control programs so that preventable nosocomial infections and their associated expenditures can be averted.