Posterior interosseous syndrome is a rare, focal neuropathy. It sometimes also, called ‘Radial tunnel’ or ‘Supinator channel’ syndromes.The most common cause is trauma, entrapment of arcade of Frosche, fibrous band, compression by tumour or ganglion, fracture, laceration are other causes. Physical examination and electrophysiological and radiographical investigations are useful for the diagnosis. We presented a case with posterior interosseous nerve paralysis with its specific and interesting electromyographic findings.