The authors reviewed 17 fractures of the olecranon apophysis in 10 children with mild osteogenesis imperfecta (OI). Seven of the 10 patients sustained the same injury to the opposite extremity 1 to 70 months (mean 15.1) after their initial fracture. Four fractures were initially treated by cast immobilization alone. Two of these eventually required operative treatment because of refracture or late displacement. In all, 15 fractures were treated operatively. All had healed at the time the cast was removed; however, two refractured. At latest follow-up (mean 53 months), no patient reported pain or limited function. Children with OI may be prone to this injury. Cast immobilization with careful follow-up may be used for minimally displaced fractures, but operative treatment is recommended for displaced fractures. The high rate of bilateral injury (70%) suggests that children with OI who sustain this fracture should be counseled regarding the risk of injury to the opposite extremity.