The posterior interosseous nerve (PIN) paralysis is characterized by weakness of the innervated muscles: the supinator muscle, the extensor muscles to the wrist, fingers and thumb (except the extensor carpi radialis longus) and the abductor pollicis longus muscle. Exploration of the nerve is recommended if there are no signs of spontaneous recovery after a period of observation of three to nine months. Another form of posterior interosseous nerve syndrome (PINS), also called the radial tunnel syndrome, presents with proximal forearm pain only. It is recommended to treat these patients conservatively at first. Only if conservative therapy does not relieve the symptoms of pain the PIN should be explored. A retrospective follow-up study of 14 patients with PINS was carried out, of which 12 patients had paresis or paralysis and two patients a pain syndrome. All, but one, were operated on. The results at follow-up will be discussed. It is recommended that the period of observation should be six to eight months for patients with PIN paresis, however, for patients with a full paralysis it is not possible to make any recommendation from this series. In contrast to the results reported in the literature, both our patients with pain as the only symptom obtained poor results at follow-up. For this group of patients the importance of the conservative treatment is emphasized.