A rare case of posterior interosseous nerve paralysis due to vascular conflict with the arcade of vessels arising from the recurrent radial artery is reported. This is one of the most unusual causes of nerve compression in the radial tunnel region. Section of the compressing arterial vessels and the external neurolysis led to the complete recovery of the motor deficit within 12 months. The surgical exploration is advisable on the basis of the clinical findings of posterior interosseous nerve deficit; the vascular nerve compression is a surgical surprise and cannot be predicted preoperatively. The outcome of the motor deficit is good, up to a complete recovery, when the nerve decompression is early and satisfactory
