The acute toxicity of norfloxacin for chickens has been studied with various routes of administration. The experiment was conducted on chickens breed Hisex Brown in oral, intraperitoneal and intramuscular injections of the drug. The study used cockerels age 14 days, which were combined in groups of 10 goals. Orally, norfloxacin was administered using a gastric probe in doses of 10005000 mg/kg body weight. The interval between doses was 1000 mg. The drug was administered intraperitoneally in doses of 100800 mg/kg body weight, the interval between doses was 100 and 200 mg. Intramuscularly, norfloxacin was injected into the pectoral muscle of chickens at doses of 400-1200 mg/ kg body weight, with an interval between doses of 200 mg. The control chickens were injected with 1 ml of isotonic sodium chloride solution, one group was intact. Chickens were observed for two weeks, changes in behavior, physiological state were taken into account, as well as death was recorded. Parameters of acute toxicity of norfloxacin for chickens were calculated according to the method of Litchfield and Wilcoxon. As a result of research, it was found that oral administration of norfloxacin to the chickens LD50 of the drug amounted to 3770 (2992÷4750) mg/kg. When intraperitoneal administration LD50 of the drug was equal to 380 (277÷520) mg/kg body weight. With intramuscular injection of norfloxacin, the LD50 of the preparation for chickens was 637 (510÷796) mg/kg body weight. Oral and parenteral administration of norfloxacin to chickens is classified as Class III toxicity - moderately hazardous substances.