Pharmacokinetics of cefuroxime was studied in patients on continuous ambulatory or intermittent peritoneal dialysis. A single intravenous bolus (15 mg/kg) of cefuroxime provided a mean serum concentration of 86 mg/litre 5 min, 40 mg/litre 1 h, 163 mg/litre 24 h after the injection. The peritoneal clearance of cefuroxime varied widely among different individuals, ranging from 1.45 to 6.17 ml/min with a mean of 3.59 ml/min during 4-hour exchanges, and from 0,52 to 11.3 ml/min during 2-hour exchanges. A single injection (15 mg/kg) of the antibiotic could not provide satisfactory antibiotic concentrations in peritoneal effluent during peritoneal lavage. When cefuroxime had been added to peritoneal dialysis solution before the solution was instilled into the peritoneal cavity, a significant decrease in cefuroxime concentration occurred in the peritoneal effluent even after a short equilibration time. Furthermore, cefuroxime concentrations measured in residual dialysis solutions in the plastic bags ranged from 44.3 to 1,351% of the concentration of cefuroxime calculated from the added doses, indicating that despite great care, mixing of the antibiotic with dialysis solutions in plastic bags was far from uniform.