Class II mechanics are supposed to affect the vertical balance of the face when they are used in hyperdivergent patterns. We carried out a study about class II mechanics effects on 100 patients ; 50 of them are hyperdivergent (GoGn/SN≥37), and 50 non-hyperdivergent. They all were treated with an Edgewise appliance without any high pull head gear. The authors showed that GoGn/SN angles and Occ/SN tend to be minored in a squeletal open-bite population. Thus, Class II mechanics can be prescribed in any vertical facial pattern.