Stress fractures of the femoral neck in athletes. The consequence of a delay in diagnosis. Twenty-three patients with stress fractures of the femoral neck were followed up at an average of 6.5 years after the injury. There were 16 recreational athletes and seven elite athletes. Most injuries (N = 15) occurred during running. The diagnosis was confirmed within 3 to 104 weeks (mean, 14 weeks) after the initial onset of symptoms. Sixteen of the patients were treated with internal fixation, the remaining seven were treated conservatively. Seven patients (30%) developed complications requiring major surgery. Five of these patients had Type 3 fractures (displaced) and four had been treated with internal fixation initially. The remaining two patients had Type 1 fractures (endosteal or periosteal callus without an overt fracture line); one was treated operatively and the other conservatively. Three patients developed avascular necrosis and two were treated by hip replacement. The third patient was treated with arthrodesis. Three refractures and one pseudarthrosis were treated by osteotomy. At followup, all elite athletes stated that they had to end their career as a result of the injury. Results were rated by the ability of the athlete to return to sports. There were 9 bad or fair results, 13 good, and 1 excellent result. No difference in activity level or subjective rating was observed between the surgically and conservatively treated group either preinjury or postinjury. The most important factor influencing the complication rate seems to be the type of fracture. The high incidence of displaced fractures (Type 3) could speculatively be caused by undiagnosed tension side stress fractures. If so, the delay in correct diagnosis may be disastrous. However, we could only objectively observe this in one of our cases. 