We looked for vertical changes in lateral cephalometric X-rays of patients who had been treated with Andresen and Häupl appliances to correct distal occlusion. Thus, a therapy using functional appliances for orthodontic correction has the following effects on the vertical proportions of the visceral cranium. 1. The alveolar processes show additional vertical growth in the area of the incisors of the upper jaw and the molars of the lower jaw. 2. In conjunction with 1, increased vertical growth of the anterior facial heights compared to the posterior facial height causes an opening of the bite which, however, is not significant in terms of the Jarabak ratio. 3. Functional therapy has an effect on the spina plane, and, in addition, causes active vertical growth in the area of both upper facial heights, i.e., of the entire nasomaxillary complex. This additional growth is a little bit more pronounced anteriorly than posteriorly. Therefore the effect of functional orthodontic appliances on the nasomaxillary complex seems to be more complex than previously believed. 4. We did not observe any additional growth in the area of the ascending rami and/or condyles of the lower jaw during activator treatment. Our studies showed that the influence of functional orthodontic therapy on the vertical growth of the lower jaw is rather insignificant; the significant vertical changes were seen in the area of the mandibular molars and of the anterior facial heights. 5. Our findings thus support the assumption that the main vertical effect of the activator can be described as a relative inhibition of the development of the nasomaxillary complex with simultaneous normal progression of mandibular growth.(ABSTRACT TRUNCATED AT 250 WORDS)