The outcome of 260 repairs of the radial and posterior interosseous nerves, graded by Seddon’s modification of the Medical Research Council Special Committee’s system, was analysed according to four patterns of injury; open ‘tidy’, open ‘untidy’, closed traction, and those associated with injury to the axillary or brachial artery. We studied the effect on the outcome of delay in effecting repair and of the length of the defect in the nerve trunk. Of the 242 repairs of the radial nerve we found that 30% had good results and 28% fair; 42% of the repairs had failed. The violence of injury was the most important factor in determining the outcome. Of the open ‘tidy’ repairs, 79% achieved a good or fair result, and 36% of cases with arterial injury also reached this level. Most repairs failed when the defect in the nerve trunk exceeded 10 cm. When the repairs were carried out within 14 days of injury, 49% achieved a good result; only 28% of later repairs did so. All repairs undertaken after 12 months failed. Of the 18 repairs of the posterior interosseous nerve, 16 achieved a good result.