Aim: Deep venous thrombosis (DVT) is an interaction between hereditary and acquired factors. Prothrombin gene mutation is one of these hereditary risk factors that may cause DVT through elevation of the Prothrombin level and therefore, requires special attention. In this study we tried to have an idea about frequency of this gene mutation in patients with DVT. 
Methods: Prothrombin gene mutation was looked for in forty Warfarin-Resistances DVT patients. The results were compared to another forty Warfarin-Sensitive DVT patients and thirty healthy blood donors. 
In addition blood samples were assessed for the levels of protein C, protein S, antithrombin III and anticardiolipin 
antibodies. 
Results: Recurrent DVT and positive family history were more frequent in the Warfarin-Resistance group. Prothrombin gene mutation was found in DVT patients as well as healthy controls, but with different percentages. The higher frequency of this gene mutation in Warfarin-Resistance individuals may confirm its mechanism in causing DVT. 
Conclusion: This study supports that Prothrombin gene mutation is present in our population, especially DVT patients. The study also suggests that patients with Warfarin-Resistance should be tested for the presence of this gene mutation.