Orthognathic surgery and adult orthodontic treatment are relatively new areas in the medical field. However, a better understanding of the historical background helps to improve today's teamwork between surgeons and orthodontists. For a (too) long period of time, the two schools have progressed in parallel; surgeons and orthodontists ignoring or criticising one another. The main change which led to the current synergy came out when specialists became aware of the importance to decompensate the alveolo dental level, in order to position correctly the basal bones of either the maxilla or the mandible. This change was not easy, especially for the orthodontists, because they were obliged to worsen the deformity even if just momentarily. During the eighties, a better reciprocal understanding of the technical possibilities in each field allowed to progressively improve cooperation between orthodontists and maxillo-facial surgeons. Consequently, as dialogue became more intense, a real "symbiosis" has arisen, based on mutual respect which did not previously exist, or rarely, about fifteen years ago.