[en] Radiation-induced changes in haemostasis in vitro and in vivo are reviewed. Particular attention is paid to the results obtained in the Department of Radiobiology and Health Protection of Institute of Nuclear Research, demonstrating: dose dependent parallel impairment of tropocollagen irradiated with moderate doses of X-rays in vitro to polymerize and to interact with blood platelets, preferential cross-linking of x-chains of fibrinogen during radiation-induced aggregation of this protein, inhibition of fibrinolysis associated with an increase in antiplasmin activity in the course of acute radiation sickness in dogs, antiheparin and fibrinoplastic properties of some alkaline, low molecular weight proteins from mammalian cells, marked and abrupt increase of heparin neutralizing ability of plasma of rabbits exposed to sublethal doses of X-rays, dose dependent release of antiheparin and fibrinoplastic substances from thymocytes irradiated in vitro, decreased susceptibility of fibrin clots formed in the presence of cellular alkaline proteins (histones) to fabrinolysis. (author)