After adding 10 mg of ceftazidime to the circulating blood of five isolated rabbit liver perfusions, total antibiotic excretion over a 3 hours period accounted for 1.4% of the administered dose; only 0.9% was found to be metabolized by the liver. In five healthy subjects given 2 g ceftazidime intravenously, 0.05% (102 +/- 576 micrograms) was recovered in the duodenal fluid over a four-hour period. In 10 patients with a T-tube inserted following cholecystectomy, 0.21% of a 2 g dose of ceftazidime injected intravenously was found in the bile collected over a 12-hour period (4 161 +/- 489 micrograms); a mean biliary peak of 36.3 +/- 4.0 micrograms/ml was recorded during the second hour. In 10 patients in whom serum, choledochal bile and gallbladder bile were sampled simultaneously during surgery 1 hour after IV administration of ceftazidime, the concentrations found were 40.6/e 2.1, 78.3 +/- 12.0 and 17.9 +/- 7.5 micrograms/ml respectively. Our results suggests that ceftazidime may be suitable in the treatment of biliary tract infections.