We reviewed the treatment and results of 22 Bennett's fractures. Of these fractures, treated by closed reduction and plaster immobilization, 20 were available for follow-up. Eighteen patients had a subjectively satisfactory outcome, and seven had a radiographically confirmed arthrosis of the first carpometacarpal joint. Of these, two were severe and painfully impaired. Nonanatomic reduction was seen in six of the seven patients with arthrosis and is thus considered a prognostic factor of posttraumatic arthrosis.