The hepatobiliary extraction profile of cefixime, a dianionic cephalosporin antibiotic, was studied in 10 patients, each of whom was provided with T-tube drainage of his or her common bile duct after cholecystectomy. After a single 200 mg oral dose, cefixime biliary clearance proved to be nonlinear, mostly in its initial phase, which is consistent with a concentrative uptake and intracellular protein binding for the drug. The latter process appears to be saturable and to operate at a rate that correlates with the total amount of cefixime recovered in the 24-hour bile drainage. Such findings seem to confirm the significant role played in vivo by hepatic ligandin in the hepatobiliary extraction of organic anions. The data also show that a single 200 mg oral dose of cefixime yields drug levels in bile substantially higher than the minimal inhibitory concentrations for the most frequent Enterobacteriaceae in biliary tract infections. Accordingly, this cephalosporin could be an interesting alternative in both prophylaxis and treatment of biliary tract infections.