The mixed dentition stage of development may provide a useful window of opportunity to embark upon orthodontic therapy to correct an isolated malocclusion or provide preliminary treatment as a precursor to more comprehensive therapy at a later stage of the patient's physical development. As in all forms of orthodontic treatment, the planning of any correction must be carried out with care so that meaningless tooth movement can be avoided. Growth modification procedures can also be considered during this stage of development but, as this is connected intimately to increased height velocity, these procedures are most usefully carried out in the late mixed dentition, or more frequently in the early permanent dentition as this coincides more closely with peak height velocity. Several studies have suggested that approximately 20 per cent of patients presenting with a malocclusion can be treated appropriately during the mixed dentition. There would appear to be a genuine risk of falling off in cooperation levels in needed, permanent dentition treatment in many patients who have experienced one or more treatment procedures at an earlier stage in dental development. These findings reinforce the need for careful treatment planning during the mixed dentition.