BACKGROUND The failure of a humeral fracture to unite after surgical treatment may be due to many factors. When there are additional complications of infection, treatment by conventional methods of internal fixation becomes very difficult. METHODS We treated 8 infected non-union of diaphyseal fracture of the humerus by the Orthofix external fixator. All had previous surgical treatment. Non-union followed plating in 6 cases and in 2 cases after the external fixator. All patients had pain, at least one sinus discharging pus and severe functional impairment of the affected arm. There were 6 men and 2 women with a mean age 40.6 years. RESULTS Bone union was achieved in all cases. The mean time to union was 4.5 months (range, 2 to 8). Patients expressed high levels of satisfaction with the outcome, despite relatively modest improvement in pain and function, mainly because of long standing infection and intractable non-union. There were no major pin tract problems requiring the removal of the Schanz screws. Radial nerve palsy developed in 1 patient who recovered spontaneously. No patient required an additional bone grafting procedure. CONCLUSIONS The use of the Orthofix external fixator without bone grafting was successful in the treatment of infected non-union of the humeral shaft. It shortened the duration of hospitalisation and immobilisation with moderate functional recovery.