Fractures of the distal humeral diaphysis are rare and have not been reported very often in the literature, although therapeutic management is more difficult than that of midshaft humeral fractures. As they are so near to the elbow, these fractures are not suitable for bracing, because pro/supination movements cannot be eliminated. Muscular forces, especially of the pronator teres muscle, force the fracture into a varus position with every supination movement. From 1974 to 1990 we treated 174 fractures of the humeral diaphysis by operative means; 31 of these were located in the distal third. According to the AO classification, 8 were graded as less difficult type A fractures, 15 as type B and 7 as type C fractures. In 22.6% of the patients primary radial palsy was present. In all, 15 fractures were treated by plating, 9 with Hackethal's bundle nails and 6 with monolateral fixators. These last patients had sustained either multiple trauma or severe soft tissue injury or both. The plated cases included 1 with non-union and with superficial infection, both in type C comminuted fractures. In 1 case the fracture was not suitable for plating, and in the other case technical errors led to failure. In the 9 cases treated with Hackethal nails there were no complications. The advantage of the method is that the nails are inserted far distant from the fracture site. Anatomical reduction is not necessary, which means there is no danger of devitalizing fragments; the technique is also quick. In the "fixator" group, we saw 1 case of non-union and 1 of refracture, both following compound fractures.(ABSTRACT TRUNCATED AT 250 WORDS)