SUMMARY Class Ⅱ elastics are usually employed in the treatment of excessive overbite and overjet with the Begg technique. The effect of Class Ⅱ elastics on bite opening and the extent of such an effect is uncertain. This article, based on measurements of 30 cases, illustrates that the effect of the vertical component of force from Class Ⅱ elastics in reducing the intrusive force generated by the anchor bands in the upper archwire is less than previously believed. The position of the circles in the archwire for intermaxillary elastics has the greatest influence on theanterior intrusive force of the upper archwire. The direction of the Class Ⅱ elastics and the lengthof the dental arch (a negative correlation) came second, while the force actually exerted by theelastics had the smallest influence. It is, therefore, suggested that the position of the intermaxillary elastic circles should be located according to the differing clinical objectives.