Summary Based on the analysis of cephalometric X-rays, dental casts and photographs of a hundred adolescent patients with osteotomies for correction of sceletal deformities of the maxillo-facial area before completion of the 17th year of age, we endeavoured to answer the following questions: 1. What are the results of orthodontic surgery in adolescence? 2. What is the relapse rate and what are the causes? 3. Is further growth of the involved bone structures impaired by osteotomies and does growth influence the results of osteotomies? 4. What are the final prognoses of these interventions, can an age limit be fixed and is it possible that further consequences can result? The following interventions were evaluated with regard to the late aesthetic result and occlusion with special reference to the questions outlined: 31 retropositionings of the mandible, 7 advancements of the mandible, 12 movements of the lower anterior segment, 20 advancements of the maxilla, 6 retropositionings of the maxillary anterior segment, 9 osteotomies of the premaxilla, 9 rotations of the small maxillary segment in cleft patients, 3 raisings of the lateral maxillary segments, 3 advancements of the midface. The results are first grouped and discussed by the type of operation. After a review of the literature treating normal growth of the face in adolescence and discussing animal experiments to influence growth by surgical interventions and after mentioning recommendations based on clinical experience, the author's own material is discussed. We have tried to illustrate the difficulties encountered in evaluating the information presented for review and analysis. The number of true relapses encountered is considered. The results are reviewed in the light of finding that 53 mandibles have grown measurably further forward post-operatively. It is concluded that post-operative growth of the mandible played an important role in the 34 clinically unacceptable late results while true relapse after operation seems to be of only secondary importance in this group of patients. Osteotomies had no influence on the growth of the mandibles. An adverse influence on growth of the maxilla could not be proved. It is clearly shown that patients below 16 years of age show significantly worse results than patients between 16 and 17 years. In boys, twice as many bad results as in girls are seen and in cleft patients, one and a half times as many as in non-cleft patients. Specific problems of the different types of intervention are discussed and it is stated that only advancement of the mandible and backward displacement of the anterior maxillary segment can be performed without risk before growth has ceased because in all other osteotomies, further growth of the mandible leads to relapse or pseudo-relapse. Finally, the different questions which were left open, are summarized and an attempt is made to show how these problems could be solved. The most important conclusion is that osteotomies of the jaws in adolescence should be deferred until growth has ceased.