Surveillance for antimicrobial resistance is the process of compiling, analyzing, and disseminating summary information on resistance to relevant antimicrobial agents in a set of target organisms. In theory, the primary purpose for conducting such surveillance is to predict the effectiveness of empiric anti-infective therapy in the individual patient and, as a corollary, to modify therapeutic recommendations when resistance exceeds threshold levels. In practice, however, it has been difficult at local and national levels to use surveillance data to modify physicians' prescribing habits. Although data on resistance patterns for organisms from a single institution are available through most hospital microbiology laboratories, these data are often not reviewed in a systematic fashion and may be compiled and published only annually. Similarly, national surveillance data on antimicrobial resistance microorganisms, especially population-based data, have been collected in the United States for relatively few organisms, and the data have not been made available to physicians or professional societies on a regular basis. Thus, timely and factual summaries on operational guidelines for prudent antimicrobial use have been sorely lacking at the local and national levels. Fortunately, this situation is changing. Data from several national surveillance systems and a growing number of regional surveillance networks are now providing a more detailed and comprehensive view of the emerging problem of antimicrobial resistance in bacterial pathogens. Locally, new laboratory information systems are providing more useful summaries of changing antimicrobial resistance patterns within an institution. The data has prompted public health agencies and professional societies to reconsider policies on antimicrobial use and infection control. For example, data, such as those on emerging vancomycin-resistant enterococci (VRE) reported by the National Nosocomial Infections Surveillance Program (NNIS) at the Centers for Disease Control and Prevention (CDC), 5 were used by the Hospital Infection Control Practices Advisory Committee to formulate guidelines on preventing the spread of VRE. 21 More recent data on Streptococcus pneumoniae are helping to shape guidelines being developed by the CDC's Drug-Resistant Streptococcus pneumoniae Therapeutic Working Group. 9 Thus, it would seem that surveillance data on antimicrobial resistance are beginning to serve their theoretical purpose. Herein, the authors review various approaches to the surveillance of antimicrobial-resistant organisms, ranging from the activities of the individual microbiology laboratory to the World Health Organization's attempts to develop a “global view” of the movement of antimicrobial-resistant strains.