The study was aimed at the experimental assessment of the efficacy of recombinant interleukin-1beta in the early therapy of haemopoiesis disorders caused by X-ray irradiation. The efficacy of the product was based on the 30-day survival rate and average life expectancy of dead animals. Endogenous and exogenous colony-formations were studied to reveal possible mechanisms of therapeutic effects of interleukin-1beta on the bone marrow. The early administration (10-15 min after exposure to radiation) of recombinant interleukin-1beta in a dose of 50 microg/kg increased the survival rate and prevented the post-irradiation decrease in the number of endogenous and exogenous CFU-S9 in irradiated mice.