Twenty-four isolated radius and ulna non-unions with segmental bone loss were operated on. Nine non-unions were in the radius, 15 in the ulna. The surgical technique consisted of removal of the necrotic bone, filling of the bone defect with an intercalary bone graft and internal fixation with a cortical bone graft fixed opposite to a plate. The average length of bone defect after freshening of the bone ends was 3.6 cm (range 2-10.5 cm). The average length of follow-up was 90 months. In 23 cases union was achieved. In three cases a postoperative infection developed. Resolution of the infection after surgical debridement was achieved in two of these patients, while recurrent infection caused failure of the treatment in the third patient. Statistical analysis revealed a shorter healing time (p = 0.031) in the ulna non-unions (12.5 +/- 3.0 weeks) compared with the radius non-unions (16.4 +/- 4.2 weeks). Functional results were classed as excellent in 10 patients, satisfactory in six, unsatisfactory in seven and failure in one.