Using a previously reported technique for bile collection, we studied the pharmacokinetics of levofloxacin (LVFX) and grepafloxacin (GPFX) in normal rats and in animals with renal failure. Continuous bile drainage was performed using normal and renal-failure Wistar rats. Oral GPFX or LVFX (40 mg/Kg) was administered. The drug concentrations in plasma, urine, and bile were determined by high-performance liquid chromatography. The area under the blood concentration-time curve (AUC) in each renal-failure rat was calculated. There were no significant differences in GPFX concentrations in the serum, urine, and bile between the renal-failure and normal rats, but the LVFX level in the urine of the renal-failure group was statistically significantly lower than in the normal group. The AUC of GPFX had an opposite correlation with the degree of renal failure, but that of LVFX was correlated.