Strictly enforced formulary restrictions for aminoglycosides, cephalosporins, and a vancomycin group generated combined savings of $2.61 (p less than 0.0046) per antibiotic day and $34,597 (p less than 0.0003) per month. Even after some cost increases (not significant) in new and other antibiotics, the program saved $1.33 (p less than 0.0175) per antibiotic day and $24,620 (p less than 0.0311) per month for all antibiotics. The pharmacy's 1985 average cost per antibiotic day and its monthly expenditures were $18.45 and $199,003, respectively. In the months following the formulary restrictions, no significant detrimental changes occurred in hospital length of stay or mortality. A retrospective analysis of 322 patients with bacteremia treated before and after the onset of the controls revealed that antibiotics were more appropriately used afterwards.