In the present study, the effect of the antibiotic, norfloxacin on the bile flow was investigated in anaesthetized guinea pigs. Intramuscular administration of the drug in a dose of 5 mg/kg body weight resulted in a 28% decrease in the bile flow. The cholestatic effect of norfloxacin was not counteracted by administration of the choleric drug, clanobutin sodium. Meanwhile administration of caffeine citrate significantly counteracted the cholestatic effect of norfloxacin. Moreover, norfloxacin has an inhibitoryeffect on the motility of isolated rabbit duodenum and induced relaxation of the isolated guinea pig ilium.