Interlocking intramedullary nailing has become the preferred method of internal fixation for diaphyseal fractures of the lower extremity. In shaft fractures of the humerus however open reduction and internal fixation with plates and screws is still considered the gold standard for operative treatment. The unreamed humerus nail (UHN) is a new implant for interlocking intramedullary nailing, which allows for stable fixation of humerus shaft fractures and immediate functional after treatment. The UHN could thus become an equal alternative to plate osteosynthesis. From this point of view we analyzed retrospectively 19 shaft fractures of the humerus, which have been treated at our institution with an UHN. Infections and iatrogenic nerve lesions did not occur. One patient with a rotational malalignment of 45 degrees underwent a secondary procedure. In two out of ten fresh fractures the bone healing failed and resulted in a non-union. In all cases of pathological fractures a good palliation could be achieved. With exception of two patients the range of motion of the shoulder and elbow was symmetric. We conclude that the UHN is a real alternative to plate osteosynthesis. Compared with most series of plate osteosynthesis published in the literature the risk for iatrogenic lesions of the radial nerve appears to be lower. Even in this small series we found however a rather high rate of non-unions.