The pharmacokinetics of ceftazidime were studied in 12 patients during peritoneal dialysis. In five patients given 1 g iv the mean serum levels (mg/l) at 0.25, 2 and 12 h after starting peritoneal dialysis were 50.6 +/- 11.2, 35.6 +/- 3.7 and 22.7 +/- 7.9, respectively. The mean ceftazidime peak level was 13.2 +/- 5.5 mg/l in peritoneal effluent, approximately 3 h after start of dialysis. The peritoneal clearance was 9 ml/min and the mean half-life during and after peritoneal dialysis was 8.7 +/- 3.1 h and 26.9 +/- 11 h, respectively. In four patients, 1 g ceftazidime was given via an intraperitoneal catheter. The mean serum levels (mg/l) at 0.25, 2 and 8 h were 14.2 +/- 3.1, 40.0 +/- 13.0 and 32.5 +/- 6.4 respectively. In three patients given ceftazidime 200 mg, in 21 dialysate treatments each with 12 cycles, mean serum levels increased from 1.3 +/- 1.5 mg/l at 1 h to 25.3 +/- 3.1 mg/l at 12 h. Mean levels in the dialysis effluent were 47.2 +/- 14.3 mg/l and the mean percentage of the dose recovered in the effluent was 47.1%. We concluded that (1) 1 g ceftazidime as an iv bolus maintained serum and peritoneal effluent levels adequate to treat patients; (2) its peritoneal absorption produced high ceftazidime levels in serum; (3) in infected patients undergoing peritoneal dialysis ceftazidime may be given either by the intravenous or intraperitoneal route.