Twenty-two patients with twenty-three fractures of the proximal part of the diaphysis of the fifth metatarsal, an injury originally described by Jones, are reported. The average follow-up was 3.5 years. Delayed union occurred in twelve (66.7 per cent) of eighteen patients treated conservatively. Four patients were operated on within two weeks of injury. The clinical picture in nine of the twenty-two patients suggested that the injury was a stress fracture. Force-platform analysis in eleven cases confirmed that the injury results from vertical and mediolateral forces concentrated over the fifth metatarsal and that it is not caused by inversion. Thirteen of the twenty-three fractures were in young athletes, often occurring during training and causing significant disability. In this group of patients, and in a select number of recreational athletes and non-athletes with delayed union, intramedullary screw fixation of the fracture is advised.