The present paper deals with studying ofhemostasis system indices after short-term (10-11 days) space flights as well as in the course of the experiment with a 7-day "dry" immersion. The following values were determined: activated partial thromboplastin time, prothrombin time, prothrombin index, international normalized ratio (INR), thrombin time (TT); fibrinogen, soluble fibrin-monomer complexes, D-dimer, plasminogen (PG) concentration; activity of antithrombin III (ATIII), protein C (PC), alpha2-antiplasmin (AP). In the 1st day after space flights a fibrinogen concentration was increased significantly as well as TT shortening tendency and fibrinolysis activation tendency were observed. There were no significant changes in ATI I11 and PC activities. During the immersion period there were no significant changes in investigated indices, with the exception of AP activity increase in 3rd day of experiment. In readaptation period, however, a decrease in ATIII and PC activities as well as PG concentration was observed. Hemostasis system response features after space flights and during immersion are probably due to different intensity and duration of external factors effects.