The pharmacokinetics of PHL-6 and interferon synthesis dynamic in the target organs (tissues) of mice were studied during its and intraperitoneal administration. In the experimental setting, there was a direct correlation between the interferon production in the murine organs with single PHL-6 and distribution of 14C PHL-6. The highest radioactivity with its oral administration was detected in the liver and intestine. Interferon was actively synthesized in the intestine, liver and serum, showing the levels of 20000, 1024-2048 and 512-1024 IU/ml, respectively. The prolonged action of the drug was in good agreement with the low PHL-6 excretion from the body. It was also shown that almost the whole radiation dose 1 (greater than 98%) was excreted with feces and urine after single and chronic administrations of uniformly labeled PHL-6 which proved important clinical drug use.