A series of 59 patients with immediate complete radial nerve palsy complicating a fracture of the shaft of the humerus was analysed. In 27 patients the radial nerve was explored and the fracture was fixed within 3 weeks of the accident. In 12 other patients exploration was performed after an average of 17 weeks. The remaining 20 patients showed signs of spontaneous recovery within 4 months and were managed conservatively. The mean follow-up time was 3 years. At exploration, laceration, interposition between the fragments or entrapment of the radial nerve in callus was found significantly (P less than 0.01) more often with longitudinal fractures of the distal third (46 per cent) than with transverse fractures of the middle third, in which 85 per cent of the explored cases showed the nerve to be no more than slightly bruised. Useful recovery was seen in 46 patients (78 per cent of the whole series).