The time and associated costs (drug, labor, supply) of administering a continuous versus an intermittent i.v. infusion of piperacillin-tazobactam were compared. The total labor cost was calculated for each regimen based on the time required for nurses, pharmacists, and pharmacy technicians to either prepare or administer the drug, according to their standard responsibilities. Thirty timed observations were made for each of the dosing formulations. Observations were conducted on separate occasions for at least four different nurses, pharmacists, and pharmacy technicians per formulation. Labor costs were calculated by multiplying the mean times recorded by the average U.S. hourly wages and local wages for these health professionals and extrapolated to encompass a 24-hour period of drug administration. The average wholesale price and hospital contract price of piperacillin-tazobactam were used to calculate the costs of both intermittent and continuous infusions. The costs for all items used in drug preparation and administration were also calculated for supplies. Basic descriptive statistics were used to evaluate the costs of the time needed to prepare and administer the different regimens. Drug acquisition costs accounted for the largest percentage of the total cost for all regimens. Analysis of labor costs revealed that nursing time accounted for the majority of the labor costs, with continuous infusion regimens being the least time-consuming and least costly administration method. Continuous-infusion regimens were more cost-efficient when evaluated on a daily basis and for the total cost of 5- and 10-day treatments. The use of continuous infusion as a means of administering piperacillin-tazobactam maximized the drug's pharmacodynamics and was more cost-efficient than intermittent infusion of the drug.