This study examined the biliary tract excretion of ofloxacin in 6 post-cholecystectomy patients with a T-tube inserted into the common duct (group A) and 6 patients during cholecystectomy (group B). The patients were given 7 oral doses of ofloxacin 200mg with a 12-hour interval between each dose. Blood and common duct bile samples were collected in group A at various time intervals after the first and the seventh dose. Blood, gallbladder wall, and gallbladder and common duct bile were collected in group B during operation, 6 hours after the seventh dose. Assays were performed by use of high performance liquid chromatography (HPLC). In group A, mean serum Cmax and half-life were 2.6 mg/L and 7.6 hours after the first dose, and 5.3 mg/L and 8 hours after the seventh dose, respectively. Mean common duct bile Cmax and half-life were 6.5 mg/L and 7.5 hours after the first dose, and 12.0 mg/L and 14 hours after the seventh dose, respectively. In group B, mean concentrations (mg/L) were 2.6 in blood, 5.3 in gallbladder wall, 24.6 in gallbladder bile and 10.1 in common duct bile, 6 hours after the seventh dose. These data suggest that ofloxacin may be suitable for the treatment of biliary tract infections.