A new antibiotic drug of cephalosporin, with marked resistance to beta-lactamase, cefoperazone (CPZ) for parenteral use was used in 10 patients with acute cholecystitis or cholangitis with cholelithiasis. CPZ was given by drip intravenous injection at a daily dose of 1 to 4 g. Clinical response was excellent in 1 case, good in 7 cases, fair in 2 cases and poor was none. Clinical adverse effect was not recognized. And CPZ in a dose of 1 g was given intravenously during the operation to 6 of those patients. Tissue specimens of different sites were taken from removed organs. The materials of A-bile and B-bile were subsequently taken at intervals. Determination of CPZ concentration was performed according to paper disk method with Micrococcus luteus ATCC 9341 strain. CPZ concentrations in the A-bile increased quickly soon after injection, and reached high level peak at 30-min. to 1 hour, then they were very slow decline. CPZ was observed in the B-bile through the gallbladder wall, and reached high level concentration comparative quickly after intravenous injection. CPZ concentration in the gallbladder wall, was directly proportional to the degree of pathological changes of inflammation. On the CPZ concentration in patients with acute cholecystitis, the concentration in A-bile, B-bile and gallbladder wall were observed extremely higher than the MIC or CPZ for Escherichia coli. CPZ therefore will be a very useful drug when used for chemotherapy of biliary tract infection.