Subclavian vein thrombosis accounts for approximately 1-2% of recorded deep venous thromboses. It may be primary or secondary, and insertion of a central venous catheter is the most common cause of secondary subclavian vein thrombosis. Traumas, anatomic abnormalities and carcinoma are important additional risk factors for secondary thrombosis. Primary thrombosis of the subclavian veins is known as Paget-Schroetter syndrome. New criteria for its diagnosis include a history of increased upper extremity use prior to onset of symptoms, the presence of a venographically demonstrated thrombus and absence of any definable causes. We describe a 42-year-old woman with a history of intensive physical exertion admitted with swelling, pain and difficulty moving her arm. The diagnosis of primary subclavian vein thrombosis was established from the history of physical effort, results of Doppler ultrasound, and exclusion of other causes of subclavian vein thrombosis. This case suggests that primary subclavian vein thrombosis should be considered in young patients with subclavian vein thrombosis after exclusion of secondary disease.