Primary subclavian venous thrombosis is more rare than secondary thrombosis. This type of thrombosis is called "effort thrombosis" or Paget-Schroetter syndrome, and develops after a strenuous effort of the superior limb. A day after a 55-year-old man got drunk and slept in the left lateral position in combination with an abducted and elevated position of the left superior limb, he became aware of swelling and an oppressive feeling in his left superior limb and was admitted 9 days later. Thrombus of the left axillary-subclavian vein was confirmed by venography, and thrombolytic therapy with urokinase was performed immediately. The left arm symptoms improved for the most part. Venography after the therapy revealed thrombolysis at the site of the axillary vein, while the subclavian vein enhanced the collateral vessel pathway. The patient was discharged on the seventh hospital day, and anticoagulant therapy with oral warfarin sodium has since been continued. This is considered to be a rare case of subclavian venous thrombosis caused by sleeping in an abnormal position with the arm outstretched.