We have compared the functional outcome after glenohumeral fusion for the sequelae of trauma to the brachial plexus between two groups of adult patients reviewed after a mean interval of 70 months. Group A (11 patients) had upper palsy with a functional hand and group B (16 patients) total palsy with a flail hand. All 27 patients had recovered active elbow flexion against resistance before shoulder fusion. Both groups showed increased functional capabilities after glenohumeral arthrodesis and a flail hand did not influence the post-operative active range of movement. The strength of pectoralis major is a significant prognostic factor in terms of ultimate excursion of the hand and of shoulder strength. Glenohumeral arthrodesis improves function in patients who have recovered active elbow flexion after brachial plexus palsy even when the hand remains paralysed.