PagetSchroetter syndrome, also referred to as "effort thrombosis," refers to primary thrombosis of the subclavian vein at the costoclavicular junction. It is the most severe presentation of venous thoracic outlet syndrome, and results in severe disability if unrecognized or improperly treated. The clinical presentation is classic, with the patient complaining of a blue, swollen, heavy, painful arm. Sixty to 80% of patients report a history of vigorous exercise or activity involving the upper extremities, and approximately 85% of patients will have symptoms within 24 hours of the inciting event. The diagnosis is usually straightforward from the history and physical examination, and duplex ultrasound is very accurate.