Purposes: The KAATSU training is performed under the reduction of muscle blood flow by a speciallydesigned belt (KAATSU belt), which induces blood pooling in capacitance vessels by restricting venous return. However, no prior studies have examined the effects of KAATSU training on haemostasis. The purpose of the present study was to investigate acute effects of KAATSU training on haemostasis including fibrinolytic responses in healthy subjects. Methods: Two protocols have been performed. (1) 6 healthy men (mean age= 48 ± 5 yr) performed KAATSU (160 mmHg) of both thighs for 15 minutes and then KAASTU training combined with low-intensity leg and foot aerobic exercises for ~10 minutes in hypobaric chamber, which mimics 8000 feet in airflight. (2) Another 7 men (mean age=30 ± 4 yr) performed leg press exercises (30 % 1 RM) with and without KAATSU of both thighs 24 h after bed rest. Blood samples were taken at rest, immediately after KAATSU, and exercises with or without KAATSU, and after exercise. For the investigation of blood fibrinolysis, determinations of tissue-type plasminogen activator (tPA) activity or antigen, plasminogen activator inhibitor (PAI)-1 activity or antigen, fibrin degradation product (FDP) and D-dimer were used. Prothrombin time (PT) and platelet counts were also measured. Results: (1) In hypobaric chamber, KAATSU by itself significantly increased tPA activity, while PAI-1 activity was unchanged. Furthermore, immediately after the exercise, tPA activity increased significantly. (2) During the exercises combined with KAATSU 24 h after bed rest, tPA antigen significantly increased, compared with control exercises, but PAI-1 antigen was unchanged. In both cases, KAATSU training did not induce fibrin formation as assessed by fibrin D-dimer and FDP. Conclusions: This study indicates that potentially favorable changes occur in fibrinolytic factors after KAATSU and KAATSU training in healthy subjects.