This report is limited to clinical studies on humans and to the treatment of children and adolescents. Treatment that includes orthognathic surgery (surgical treatment of severe malocclusions) has been excluded. All types of studies, quantitative as well as qualitatatve, that concern assessment of the risks of no treatment and different aspects of treatment decisions were included.Scientific evidence for conclusions concerning the validity (that is, if a tool measures what it is intended to measure) of morphological priority indices (indices based on deviations in the bite and the dental arch from an established norm) are lacking.