VEGF, a potent mitogen for endothelial cells, is one of the most important cytokines responsible for stimulating angiogenesis. Some data confirm an important role of VEGF in wound and bone healing. In the blood, VEGF is present in plasma and, as important intracellular pool, in neutrophils and platelets. Intracellular VEGF is released to the serum upon these cells activation during coagulation. Low-molecular weight heparins (LMWHs) are routinely used as anti-coagulants for prophylaxis after bone surgery. In the previous study, performed in seven patients after orthopedic surgery, we have found that enoxaparine injections administered during post-operative two weeks, have increased angiogenic activity and VEGF level in their sera. To elucidate the origin of this cytokine, in the present study we compared VEGF level in matched plasma and serum samples collected from 12 persons before, and 14 days after surgery and daily enoxaparine (40 mg) injections. The results were also compared to the findings obtained for sera collected from 30 healthy blood donors. Both serum and plasma samples collected after enoxaparine treatment presented higher in vivo angiogenic activity in mouse cutaneous test than before administration of this drug. No differences in plasma VEGF were observed. However, VEGF concentration in matched sera samples was significantly higher after surgery and enoxaparine treatment than before the beginning of the study. Conclusion: intracellular VEGF, released during coagulation process plays an important role in in vivo angiogenic activity of serum, and its concentration significantly increased after 2-weeks enoxaparine treatment.