In this article a young, still growing female patient with a Class II division 1 malocclusion and a short mandible is presented. She was treated with functional and fixed orthodontic appliances. During orthodontic treatment with fixed appliances, mandibular lengthening by means of the intra oral distraction technique was used to correct the jaw relation. The orthodontic treatment could be finished successfully after lengthening of the mandible. The results are presented. In the discussion some alternatives for mandibular distraction are mentioned. It was concluded, that intra oral mandibular distraction is useful and successful, in selected cases.