In the present study 24 hospitalized patients requiring empirical antibiotic treatment were randomly assigned to receive the beta-lactam antibiotic/beta-lactamase inhibitor combination piperacillin-tazobactam either as an intermittent or as a continuous infusion. According to pharmacokinetic modelling, the daily dose was reduced by 33% in patients receiving continuous infusion compared with intermittent infusion. Dose reduction because of impaired renal function was required in the intermittent dosing group for 5 of 12 patients compared with 1 of 12 patients in the continuous infusion group. However, the mean daily dose in the continuous group was 15% less than the intermittent infusion group. Mean serum concentrations of piperacillin were to 39.0 microg/ml after the end of bolus distribution, exceeding by far the minimal inhibitory concentration of the most clinically relevant pathogens. The corresponding mean value for tazobactam was 6.3 microg/ml. Pharmacokinetic/pharmacodynamic modelling suggests that both treatment schemes should produce virtually identical anti-infective responses to sensitive, intermediate and resistant strains. In the present study the continuous infusion of piperacillin/tazobactam provided adequate antibacterial activity over the 24-h dosing period and offers the potential for a substantial reduction in the total daily dose.