Nosocomial infections are estimated to involve more than 2 million patients annually (1, 2) and in 1992 cost more than $4.5 billion (3). Adverse consequences of nosocomial infections and their associated costs vary by type of infection (Table 1) (3). Hospital-based programs of surveillance, prevention, and control of nosocomial infections were developed during the 1950s and refined in the United States during the 1960s and 1970s. However, questions regarding the efficacy and cost-effectiveness of these programs have persisted. This report examines knowledge about the effectiveness of nosocomial infection surveillance, prevention, and control and their cost-benefits.