Venous leg ulcerations are mostly caused by chronic venous insuffeciency dealing with trauma, thrombophlebitis or thrombotic syndrome. Various risk factors have been identified for the development of deep venous thrombosis. Activated protein C resistance has recently emerged as one of the most frequent causes of venous thrombosis. Activated protein C cannot inactivate thrombosis formation in the factor V Leiden mutation. Here we present a 23-year-old male patient with factor V Leiden mutation and activated protein C resistance. The algorythmic approach to investigate the etiopathology of the leg ulcers is emphasized.