A study based on the Burlington and Ann Arbor longitudinal samples compared selected dento-facial characteristics in cases with predominantly vertical and horizontal growth directions at the chin. The investigation tested a number of hypotheses on possible relationships between the chin growth direction and the dento-facial variations studied. It was found that cases with vertical and horizontal growth differed in several respects, the former showing greater facial height, a more retrognathic chin, a steeper mandibular plane, a larger gonial angle and less skull base flexure than the latter. In the Burlington sample, cases with vertical growth had comprehensive orthodontic treatment more often than horizontal cases.