The biliary excretion of cefuroxime was studied experimentally, using a preparation of isolated rabbit liver (n = 5) perfused in vitro during 3 h; 0.92% of the cefuroxime (10 mg) added to the circulating blood was found in the bile, while peak antibiotic activity reached a mean value of 8.0 ± 1.1 μg/ml. In man, 1 h after a single intravenous injection of cefuroxime (0.5 g), a maximum concentration of 4.0 ± 1.6 μg/ml was found in the duodenal aspiration fluid collected from 5 healthy subjects. In 10 patients with T-tube drainage, a mean biliary peak of 10.3 ± 2.4 μg/ml was observed 2 h after intravenous injection of the same dose; the biliary excretion of cefuroxime during the 12-hour experiment corresponded to 0.13% of the administered dose. Assays performed during cholecystectomy in 10 patients 1 h after cefuroxime intravenous injection of 0.5 g showed concentrations of 11.9 ± 0.8 μg/ml in the serum, 12.0 ± 1.5 μg/ml in the common duct bile and 7.4 ± 1.1 μg/ml in the gallbladder bile. These results were compared with those observed after administration of 11 other β-lactam antibiotics in identical experimental and clinica