In a group of 47 healthy men aged 25-55, the influence of moderate, exhaustive, and prolonged exercise on blood platelet function, coagulation, and fibrinolytic activity was evaluated. Static exertion of short duration and moderate intensity did not cause significant alterations in any of the indices analyzed. Prolonged exercise (60 min) performed on a bicycle ergometer in aerobic conditions led to strong activation of the fibrinolytic system [euglobulin lysis time (ELT) fell from 208 to 88 min] and a slight increase in platelet count (PC) but did not cause significant changes in platelet factor 4 (PF 4) and platelet aggregate ratio, recalcification (RT), and prothrombin time (PT). Repeated bouts of maximum exercise leading to considerable acidosis (pH = 7.22; BE = -13.3) caused a significant increase in blood platelet count and an increase in PF 4 release. These changes were accompanied by strong intensification in fibrinolytic activity (over 63% reduction of ELT and a marked increase of fibrin/fibrinogen degradation products). In some individuals, unfavorable hemostatic changes were observed following intensive exercise. It is concluded that more attention should be given in future to the problem of verification of preventive and rehabilitative training programs from the point of view of exercise-induced hemostatic changes.