To investigate possible associations between ABO blood system and coagulability levels, fibrinolysis, total lipids, cholesterol, and triglycerides, the plasma and serum of 300 Rh-positive male blood donors were tested. The tests performed were: RT, PTT, K-PTT, PT, F.V, F.II, F.VII, Complex II, VII, and X, TGT, fibrinogen, HAE 0.2, HAE 0.5, ELT, LIP, Col.1, Col.2 and TRI. Analysis of the laboratory data shows a lower coagulability in O blood group individuals. This result was obtained in coagulation tests (RT, PTT, and K-PTT) specific for factor VIII level. In addition, a higher sensitivity to the in vitro heparin anticoagulant effect in O group individuals was confirmed. Nevertheless, these conclusions are specific for Negroids, the same effects not being observed in Caucasians. None of the other laboratory tests revealed any differences related to either blood group or race.