The clinical efficiency of the an bio c is determined by its distribu on in organs and ssues, the ability to penetrate the physiological and pathological barriers of the body. The ar cle presents the results from a study of the intake, distribu on, and excre on of doxycycline hyclate -the ac ve substance of the an bio c pollodoxin from the body of broiler chickens (the Cobb-500 cross) with ornithobacteriosis.It has been established that 24 hours a er the pollodoxin solu on applica on in broiler chickens with ornithobacteriosis, the highest content of its ac ve substance (doxycycline hyclate) was found in the lungs, liver, slightly less -in the kidneys, and least -in the heart and pectoral muscles. A er 48 and 72 hours, the content of doxycycline hyclate increases in the liver, kidneys, heart, and pectoral muscles compared to 24 hours, while in the lungs decreases slightly a er 48 hours and does not differ from it a er 72 hours. At 96 hours, the content of doxycycline hyclate in the kidneys, lungs, and pectoral muscles reaches maximum values; in the liver it is smaller than the previous one (72 hours), while in the heart it does not differ from it. Doxycycline hyclate does not show cumula ve proper es and "organ affilia on" during 96 hours of entry into the body of broiler chickens with ornithobacteriosis. A er 24 hours of discon nua on of pollodoxin use (120 hours of the experiment), the content of doxycycline hyclate