The effect of static magnetic field of induction 0.005 T, 0.12 T and 0.3 T applied in daily rhythm (one hour every day) for the period of 2 weeks and 4 weeks produces an increase of FDP level in the serum. Especially, the effect elicited by the magnetic field applied 2 weeks prior to experimental thrombosis development. The range of changes was related to the duration of the exposure to the magnetic field. No dependence of the degree of induction of the magnetic field was established.