Aim — the objective of the present work was to analyze the data obtained in a study involving a group of patients presenting with recurrent deep vein thrombosis and/or bleeding who had been treated with the use of vitamin K antagonists. Material and methods. A total of 116 patients presenting either with recurrent deep vein thrombosis (n=10) or bleeding that developed while patients had been on the therapy with vitamin K antagonists were enrolled in the study. We performed clinical and instrumental examination as well as laboratory testing of the hemostatic system. All the patients received warfarin during 6 months or longer with 32 of them taking this medication to prevent deep vein thrombosis and the remaining 84 for the treatment of various cardiac diseases. The results of the clinical, instrumental, and laboratory studies provided a basis for the choice of the treatment strategies. Results. Sixty seven of the 116 patients were treated non-surgically while 27 patients were operated (25 urgently and two within 2 days after the admission to the hospital). 20 patients underwent endoscopic hemostasis, in two others the hematoma was punctured under ultrasound guidance. Eight patients presenting with recurrent deep vein thrombosis received the conservative treatment reduced to the correction of anticoagulation therapy (they were first switched from warfarin to heparins with the subsequent resumption of warfarin treatment using the individually adjusted doses of the drug). Two patients with free-floating thrombi in the main veins required the surgical intervention to prevent pulmonary embolism. The conservative treatment of the patients with bleedings included the withdrawal of warfarin together with the simultaneous administration of vitamin K1, fresh frozen plasma, and prothrombin complex concentrate in different combinations taking into consideration the results of clinical examination and laboratory testing. The conservative treatment was successful in all the cases. No severe complications, life-threatening conditions or death were documented. Conclusion. The patients receiving vitamin K antagonists are at enhanced risk of both a relapse of venous thromboembolism and bleedings. The timely started and appropriate management can prevent the severe complications.