Formulary controls are the most common and probably the most effective method for controlling abuse of antimicrobial agents in hospitalized patients. Such programs may include restriction of both the number of agents available and the way these agents may be used. These programs have been demonstrated to control pharmacy expenditures. Other potential advantages include reductions in the incidence of adverse drug reactions and the antimicrobial resistance among the hospital flora, and improvements in the overall quality of prescribing of antimicrobials. There are few data to document such benefits, however. Potential disadvantages are also poorly documented but include inconvenience for prescribing physicians, increased administrative costs, prescribing errors, and increased antimicrobial resistance. Antimicrobial control programs will likely remain common, but the availability of new information technologies should enable a transition to systems based on concurrent assessment of antimicrobial appropriateness with immediate feedback to the prescribing physician.