Antimicrobial stewardship programs (ASPs) optimize antimicrobial use to decrease the incidence of infection with multidrug-resistant organisms (MDRO) and the emergence of drug resistance, to improve patient outcomes and safety, and to decrease hospital costs. ASPs achieve these goals through several types of interventions that can occur before or after the antimicrobial has been prescribed; interventions can also be "active" or "passive." We believe that active post-prescription interventions such as post-prescription audit and feedback have the most supportive evidence and most promise. Stewardship activities must be integrated into already established efforts for infection prevention. We believe it is critical that antimicrobial stewardship, infection control, pharmacy, information technology, and clinical microbiology work collaboratively in order to decrease the incidence of infection due to MDRO.