Genetic mutations of the coagulation factors II and V (G20210A and G1691A - factor V Leiden)--as well as the one for methylene tetrahydrofolat reductase's (MTHFT) gene C677T are diseases with dominant autosomal transmission characterized by thromboembolic events leading to deep vein thrombosis and/or pulmonary embolism. The authors show the clinical observation of 2 cases of recurrent deep venous thrombosis evolving with pulmonary embolism in patients with genetic defects of the coagulating factors. The positive diagnostic was put on the paraclinical findings and the etiology was established from the homocysteine genetic modification of the G20210A prothrombin and factor V Leiden and MTHFT mutation. Publishing these cases will allow us to emphasize the importance of the genetic factors for thromboembolic episodes and especially for the consequences of the long-term anticoagulant therapy.