Avulsion fractures of the pelvic apophyses are fairly uncommon injuries. Most of these fractures occur in adolescent athletes. Traditionally they have been treated non-operatively with good results. We describe two cases of avulsion of the anterior superior iliac spine, which occurred coincidentally during a running competition at a Lille-hammer school in June 1996. The two fifteen years old boys were both treated with open reduction and internal fixation of the fragment. After three weeks they could walk normally. After 7-8 weeks they had resumed their usual sports activities, without any limitation of their sporting ability. Only a few case reports have been published dealing with operative treatment of avulsion fractures. It seems, however, that operative treatment might reduce the time to full recovery. For this reason, operative treatment of avulsion fractures should be considered for athletes and for other patients requiring a short period of rehabilitation.