Blood levels of vascular endothelial growth factor, the main marker of angiogenesis activity, and coagulation hemostasis were studied in CDF1 mice with transplanted P-388 lymphocytic leukemia. Blood levels of vascular endothelial growth factor increased by 168% in mice with tumors. The animals developed the hypercoagulation syndrome manifesting in shorter activated partial thromboplastin time and prothrombin time and development of hyperfibrinogenemia.