Although 90% of the surgical procedures performed on patients with OI are on the lower limbs, intramedullary fixation of the humerus may at times be indicated also in the upper limb for the correction of deformity and improvement of function. Upper limb deformities are generally present only in patients with severe disease (osteogenesis imperfecta congenita or osteogenesis imperfecta tarda I). The recommendations expressed in this paper are based on experience with 36 intramedullary rod fixation procedures on the upper limb in 12 patients with osteogenesis imperfecta, including 24 on the humerus, five on the radius and seven on the ulna. A Rush pin provided satisfactory fixation for the humerus, when inserted from its proximal end. Intramedullary rods were extremely difficult to insert in the forearm bones, and the author considers the operation to be rarely indicated. Two interesting and unusual problems in the upper extremities have been encountered in patients with osteogenesis imperfecta: deformity of the clavicle severe enough to cause pain and limited motion, and unicameral bone cysts in the upper humerus.