The clinical history and operative findings in a group of 29 patients who underwent reoperation for thoracic outlet syndrome (TOS) are presented. Recurrence of TOS following initial surgical treatment was found to be operation-related (retained first rib segments, regrowth of periosteum), postoperation-related (infection, too early mobilization), or trauma-related. Recurrent TOS may be classified by the location of brachial plexus fixation. In recurrent lower tract TOS the plexus is fixed to the chest wall at the level of the first rib; in recurrent upper tract TOS the plexus is fixed in the neck by the reattached anterior scalene muscle. Surgical treatment of recurrent lower tract TOS involves neurolysis, removal of retained first rib segments or regenerated periosteum, and interposition of a fat-pad pedicle graft between the plexus and the chest wall. Treatment of recurrent upper tract TOS involves scalenectomy, neurolysis, and coverage of the plexus by healthy fat.