When five normal subjects were given ceftazidime 2 g iv, antibiotic concentrations in aspirated duodenal fluid increased progressively during 4 h to a value of 21.2 ±9.2 mg/l (mean ±S.E.M.); 0–05% of the dose given was recovered in duodenal fluid. The same dose was given to 12 patients with an external biliary drain. The mean peak ceftazidime concentration of 36.3 ±4.0 mg/l was reached in the collected bile during the second hour after administration. The 12-h biliary recovery was 0–21% of the dose. The respective ceftazidime concentrations in choledochal and gallbladder bile sampled peroperatively in ten patients 1 h after ceftazidime 2 g iv were 78.3 ±12.0 and 17.9±7.5 mg/l. These data compare favourably with the results achieved with other β-lactam compounds.