Blood coagulation and fibrinolytic variables were investigated with recently developed laboratory methods during normal pregnancy, at delivery and during puerperium. The state of hypercoagulability was registered by an increase in activity of factors XII, X and VIII, in VIII antigen, in ratio between VIII antigen and activity as well as in fibrinogen. Activation of blood coagulation at delivery results in decreasing levels of factors XII and XI and an increase in fibrinopeptide A. However, normal mean values of antithrombin and platelets were observed. An increase is noted in the plasminogen level as well as in urokinase inhibitor during pregnancy. In addition alpha 2-antiplasmin and prekallikrein were studied; however, no marked changes were noted.