Normal facial growth displaces maxilla and mandible forward and downward. The result is the skeletal and facial equilibrium described by Angle. In classe-II and class-III cases, growth patterns are modified as well as sagittal and vertical dento-facial dimensions. Development and differential diagnosis of skeletal and dental class-II cases are presented, in relation to their sagittal parameters only. The evolution of a class-II can be predicted with the help of several cephalometric measurements, so that the adequate therapy can be used in time to reestablish proper growth.