A review of thirty-five patients who had a fracture of the coronoid process of the ulna revealed three types of fracture: Type I--avulsion of the tip of the process; Type II--a fragment involving 50 per cent of the process, or less; and Type III--a fragment involving more than 50 per cent of the process. A concurrent dislocation or associated fracture was present in 14, 56, and 80 per cent of these patients, respectively. The outcome correlated well with the type of fracture. According to an objective elbow-performance index used to assess the results for the thirty-two patients who had at least one year of follow-up (mean, fifty months), 92 per cent of the patients who had a Type-I fracture, 73 per cent who had a Type-II fracture, and 20 per cent who had a Type-III fracture had a satisfactory result. Residual stiffness of the joint was most often present in patients who had a Type-III fracture. We recommend early motion within three weeks after injury for patients who have a Type-I or Type-II fracture. Reduction and fixation, followed by early motion when possible, may be the preferred treatment for patients who have a Type-III fracture.