Klippel-Trenaunay-Weber syndrome (KTWS) is a congenital disorder characterized by cutaneous capillary malformations, venous-lymphatic anomalies, hypertrophy of soft tissue and bone in the area of increased vascularity and arteriovenous fistulas with shunting. In this article we report the case of a 25 year old man with KTWS who had multiple surgical operations because of arteriovenous malformations. He admitted with pulmonary embolism attack to the hospital although he was taking prophylactic heparin treatment. We evaluate the risk of pulmonary embolism in patients with KTWS, being aware of the risk of deep venous thrombosis in progress of the disease and the importance of early diagnosis in prognosis.