Objective. To analyze significance of hereditary thrombophilia in development and complicated course of idiopathic acute venous thrombosis of the lower limbs. Material and methods. There were 79 patients (53 men and 26 women) aged 47.6 years with acute venous thrombosis of the lower extremities and pelvis. Molecular genetic analysis of blood for markers of hereditary thrombophilia was performed in long-term period after primary treatment of acute venous thrombosis using real-time polymerase chain reaction. Polymorphisms of the gene of hemostatic and folate cycle factors were determined: F2:20210, F5:1691, FGB:-455, PAI-1:-675, PLAT, ITGA2:807, ITGB3:1565, MTHFR:677, MTRR:66. The control group included 27 patients without acute venous thrombosis. In 62 patients, serum homocysteine was determined by photometric method. Incidence of recurrent venous thromboembolic complications (VTEC), severity of chronic venous insufficiency and recanalization of thrombosed veins were compared in long-term period. Results. Patients with idiopathic acute venous thrombosis of the lower extremities were characterized by common polymorphisms of PAI-1 (77.2%), ITGA2 (67.3%), MTRR (62.2%), FGB (57%), MTHFR (45.5%) genes. F2:20210 and F5:1691 gene mutations were found in 7.6% and 15.2% of patients, respectively. Recurrent VTEC was recorded in 27 (60%) out of 45 patients with multicomponent thrombophilia (4 or more polymorphisms of genes and mutations regardless of their type, i.e. hetero- or homozygote). Moreover, 2 or more episodes of VTEC occurred in 10 (22.2%) of these patients (p<0.001). Conclusion. Complicated course of idiopathic acute venous thrombosis may be associated with multicomponent thrombophilia.