The authors of this paper discuss upper extremity in children with osteogenesis imperfecta: fractures frequency, presence of the deformity, radiological data as well as ability to use the limb. Fractures of the upper extremity and shoulder ring occurred in 93 (66%) among 141 children with oi that were treated in the ward in years 1988-2002. Most of the fractures occurred in children with type III oi in Sillence classification, this was a group were deformities appeared most frequently. Generally, deformities were found in 33% of the children with oi. Typical arm deformity was posterior bending, in forearm dorsal bending. Varus elbow occurred often (11%). We found in the x-rays capitis radius dislocation (3.5%), interosseus membrane ossification (2.1%), pseudoarthrosis of the forearm bones (2.1%). The causes of the deformities and opportunities to prevent them were discussed.