The effect of a program designed to reduce hospital drug costs by limiting the selection of injectable cephalosporins and promoting the rational use of the selected agents was studied. Cefazolin sodium was chosen as the primary injectable cephalosporin, and guidelines for proper dosing were approved. Strict guidelines for the use of cephapirin sodium, cefamandole nafate, and cefoxitin sodium were also adopted; cephalothin sodium was deleted from the formulary. Clinical pharmacists reviewed all cephalosporin orders and consulted with prescribers whose orders did not conform to the guidelines. Total cephalosporin purchases for the first fiscal year of the program were $64,914, a decrease of $55,715 or 46.2% from the previous year's total of $120,629. Cost per patient day for cephalosporins decreased from $0.921 to $0.519 (43.6%) over the same period. The number of milligrams of cephalosporins used per patient day decreased from 398.16 to 178.77 (55.1%), while the number of patient days decreased by only 4.45% during the same interval. The estimated annual cost of monitoring the program was $1500. This program demonstrates that substantial cost savings can be achieved if guidelines for the use of injectable cephalosporins are clearly outlined and strictly enforced.