Patients with critical illnesses requiring aggressive medical intervention are at risk of acquiring serious nosocomial infection that may lead to increases in medical expenditures, morbidity, and mortality. Infection control in this population entails continuous surveillance for hospital acquired infection, with investigation of outbreaks. Policies for effective antibiotic utilization, disinfection of medical devices and hospital environment, and patient isolation may limit nosocomial infection in this population. Finally, an effective infection control program should protect the health care worker from hospital-acquired infections through educational programs, routine health surveillance, vaccinations, and post-exposure care.