Patients hospitalized in ICUs are 5 to 10 times more likely to acquire nosocomial infections than other hospital patients. The frequency of infections at different anatomic sites and the risk of infection vary by the type of ICU, and the frequency of specific pathogens varies by infection site. Contributing to the seriousness of nosocomial infections, especially in ICUs, is the increasing incidence of infections caused by antibiotic-resistant pathogens. Prevention and control strategies have focused on methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, and extended-spectrum beta-lactamase-producing Gram-negative bacilli, among others. An effective infection control program includes a surveillance system, proper handwashing, appropriate patient isolation, prompt evaluation and intervention when an outbreak occurs, adherence to standard guidelines on disinfection and sterilization, and an occupational health program for health-care providers. Studies have shown that patients infected with resistant strains of bacteria are more likely than control patients to have received prior antimicrobials, and hospital areas that have the highest prevalence of resistance also have the highest rates of antibiotic use. For these reasons, programs to prevent or control the development of resistant organisms often focus on the overuse or inappropriate use of antibiotics, for example, by restriction of widely used broad-spectrum antibiotics (e.g., third-generation cephalosporins) and vancomycin. Other approaches are to rotate antibiotics used for empiric therapy and use combinations of drugs from different classes.