Changes in the venue of health care have been remarkable during the past decade. Recent estimates indicate that 60% of surgical procedures in the United States are now performed in ambulatory surgical settings. 72 Complex surgical interventions that 10 years earlier would have been unthinkable outside the confines of hospitals are being performed in ambulatory facilities. Similarly, the management of complex medical conditions has been successfully transferred from hospitals to ambulatory care settings. Finally, hospital admissions for patients with acute medical conditions associated with asthma and congestive heart failure, previously an indicator of optimal care, are now considered indicators of suboptimal ambulatory care. Competition and diminishing resources have compelled health care systems to build infrastructures to support ambulatory care and reduce the need for expensive hospitalization. The changing venue of health care should theoretically reduce the risk for nosocomial infections. There is a paucity of published information, however, describing the impact of the shift to ambulatory care on the risk for infections related to medical and surgical interventions. The purpose of this article is to review the risk for and control of nosocomial infections associated with ambulatory care. Nosocomial infections have traditionally been defined as infections originating in hospitals. For the purpose of this review, the term nosocomial infection encompasses any infection that occurs in association with health care, regardless of site. Ambulatory care in this context includes health care rendered for acute and chronic diseases and surgical interventions performed in facilities in which patients reside for less than 24 hours. Risk for nosocomial infections associated with care in emergency departments, dialysis centers, chronic care centers, and in the home are not considered in this review. The discussion considers four topics: (1) the theoretical risk for nosocomial infections in ambulatory care is discussed relative to the risk for infections among hospitalized patients; (2) selected pathogens that pose a risk for transmission in ambulatory settings is described; (3) procedures that are performed frequently in ambulatory care venues and that pose a risk for infection is discussed; and finally, (4) considerations regarding the environment and recommendations for controlling the risk for transmission of infections in ambulatory sites is discussed. The general lack of empirical studies regarding the risk, detection, and efficient control of nosocomial infections in ambulatory care environments will be apparent to the reader.