A 36-year-old woman was referred to the thoracic surgery clinic after she had presented with a 3-week history of swelling and bluish discoloration of the left arm and hand that occurred when she raised her arms (Panel A). The symptoms started after she had spent 10 days typing at a desk. Computed tomography of the chest identified no thromboses, and venography was subsequently performed. When the patientโs arms were down at her sides, blood flowed through a normal subclavian vein on the right side (Panel B, arrow). On the left side, blood flowed through an anatomical variant of the subclavian vein that connected to the jugular veins (Panel B, arrowhead). When the patientโs arms were elevated, blood flow through the subclavian veins on both sides was limited by compression between the first rib and the clavicle (Panel C, arrows); blood drainage from the left side was slower owing to smaller collateral vessels (box), which accounted for the patientโs symptoms on the left side. A diagnosis of venous thoracic outlet syndrome was made. Venous thoracic outlet syndrome occurs when the subclavian vein has thrombosis or is compressed in the costoclavicular space. In this case, the patientโs excessive desk work was thought to have caused tightening of the neck muscles that restricted a previously narrow costoclavicular space. A physical therapy program was prescribed. At the 3-month follow-up, her symptoms had abated.