1. Most open-bites are deficient in growth of the upper face and in growth of the posterior face. However, some varieties have adequate posterior face height. A compensatory increase in lower anterior face height occurs in both types. 2. The ratio of upper anterior face height to lower anterior face height (UAFH/LAFH) is suggested as an aid in determining the prognosis for the orthodontic correction of anterior open-bite. 3. The treatments of eight patients were presented to illustrate this concept. The results were critically analyzed. 4. The validity of this index can be determined only after prolonged use by many orthodontists.