Multi-region time and motion studies were conducted in hospitals of various sizes to determine the cost of personnel and supplies associated with the preparation, dispensing, and administration of reconstituted parenteral antibiotics. The administration systems studied included the piggyback intravenous admixture (including several batch methodologies), the volume control intravenous set, and intramuscular techniques. Supply costs were calculated for each system. Projections of potential cost savings resulting from decreased administrations of parenteral cephalosporins were calculated for surgical prophylaxis, 10-day treatment course, and average per bed hospital use. The projected cost savings for the first 24 hours of surgical prophylaxis, or a 10-day treatment course changing from every eight- to six-hour dosing to a single daily dose ranged from $5.60 to $24.25 and $28 to $145, respectively. The average hospital's projected cost savings potential per hospital bed resulting from decreased administration of parenteral cephalosporins depended on the administration system or systems used and ranged from $35 (25 percent reduction in doses) to $364 (75 percent reduction in doses). An algorithm is presented for individual hospitals to use in calculating cost containment estimates. Clinicians and health care managers should seriously consider the cost containment advantages provided by the substitution of newer antibiotics which permit reduced administration frequency.