The Russell-Taylor intramedullary interlocking nail has been used on 39 patients with fractures that occurred at various levels of the humerus. Thirty patients had acute fractures and nine had pathological fractures. Twenty-five patients with acute fractures were re-examined after their fractures had united and assessed according to Neer's classification of shoulder function. Twenty-two (88 per cent) had excellent and satisfactory shoulder function. Pain relief was achieved in all pathological fractures. Shoulder pain encountered in a few patients in this series, where nailing was performed by the antegrade route, was mainly due to problems associated with the proximal interlocking screw.