Ceftazidime, a new parenteral third generation cephalosporin, is widely used because of its broad aerobic gram-negative bacterial coverage and its apparent low risk of toxicity. To establish the effect of hemodialysis on the elimination kinetics of ceftazidime and to determine the supplementary dose of the drug after each dialysis session, we studied nine anuric patients with end stage chronic renal failure undergoing hemodialysis. After a single 1 g intravenous bolus injection of ceftazidime a two-compartment open model was used to calculate the pharmacokinetic parameters. The mean ceftazidime concentrations in hemodialysis patients were 64.3 micrograms/ml at the start of dialysis and 20.0 micrograms/ml at the end of dialysis session. A 4-h hemodialysis procedure reduced the area under concentration vs time curve from 795.1 mg/l X h to 175.8/l X h and the elimination half life of ceftazidime from 33.6 h to 3.3 h. Dialyzer clearance was 55.6 ml/min and 55% of the administered dose was recovered in the dialysate fluid. Hemodialysis patients should receive a supplemental dose equal to half their usual maintenance dose immediately after each dialysis session.