Twenty-three patients who had a clavicular non-union were treated operatively at the Massachusetts General Hospital from 1974 to 1985. Twenty-one non-unions were the result of fracture and two, secondary to osteotomy. Twenty non-unions were located in the middle third of the clavicle, while three were in the lateral third. Radiographically, eighteen non-unions were atrophic and three, hypertrophic. Two non-unions resembled pseudarthrosis. Of the etiological factors that were reviewed the extent of displacement of the original fracture was the most significant. Associated complications of the non-union included limited mobility of the shoulder in fourteen, neurological symptoms in eight, thoracic outlet syndrome in four, and arterial ischemia in one. Of the nineteen patients who were treated to obtain union, seventeen had a successful result at an average length of follow-up of 23.8 months. In sixteen (93.7 per cent) of the seventeen patients union was achieved by fixation with a plate; one patient required two procedures. Ancillary bone graft was used in eighteen patients, with three requiring a sculptured bicortical graft from the iliac crest to span a defect. Of the four other patients three were treated with a partial clavicular resection and one, with complete clavicectomy.