Exposure of rabbits to constant magnetic fields of induction 0.005, 0.12 and 0.3 T for 1 h daily leads to a significant acceleration of the thrombolytic process. A considerable shortening of the time duration needed for liquefaction of the clot was observed. A halved (7 d) duration of the thrombotic process in relation to the control test (14 d) was established in animals exposed for 14 d to magnetic field action before the origination of clotting, with continued exposure to the magnetic field to the moment of clotting recession. The changes were not dependent on the intensity of the magnetic field.