To determine appropriate doses of cefuroxime and ceftazidime for septic patients with acute renal failure (ARF) treated by continuous arteriovenous haemodialysis (CAVHD), we performed pharmacokinetic studies in patients receiving these antibiotics. All patients were treated by CAVHD using Hospal AN69S 0.43 m2 filters and Fresenius 1.5% peritoneal dialysis fluid at dialysate flow rates (Qd) of 1 and 21/h. Patients received cefuroxime 500 mg (n = 11) or 750 mg (n = 1), or ceftazidime 500 mg (n = 9) i.v. 12-hourly and all studies were done at steady-state. For cefuroxime, volume of distribution (Vdarea) was 22.8 ± 3.5 l, terminal elimination half-life (t½) 12.6 ± 2.2 h and total body clearance (TBC) 22.3 ±3.0 ml/min (mean ± SEM). Mean sieving coefficient (SC) was 0.90 ± 0.12 and filter clearances at Qd 1 and 2 l/h were 14.0 ± 2.3 and 16.2 ± 3.4 ml/min respectively. For ceftazidime, Vdarea was 31.1 ± 6.51, t½ 14.7 ± 3.3 h, and TBC 24.8 ± 0.8 ml/min. Mean SC was 0.86 ± 0.03, and filter clearances at Qd 1 and 2 l/h 13.1 ± 1.2 and 15.2 ± 1.5 ml/min. Satisfactory plasma concentrations of both antibiotics were maintained in all patients during treatment. These data suggest that cefuroxime 500–750 mg and ceftazidime 500 mg 12-hourly are suitable doses for patients with ARF treated by CAVHD.