The authors present the method of predicting the body height of patients with achondroplasia in adulthood and the method of predicting shortening of the lower segment of the body as compared to the trunk. They evaluate a group of 12 patients with achondroplasia at the age from 3 to 17 years. They compare the growth curves of patients with normal Czechoslovak population and with a group of American patients suffering with achondroplasia. The application of growth curves of American patients with achondroplasia appears to be the most suitable and simple graphical method for the prediction of the body height of the Czechoslovak patients suffering from achondroplasia. The method of the prediction of dwarfism of the lower segment of the body has been developed for the purpose of the rational indication of the stepwise prolongation therapy by the compression-distraction method. Analogically it will be possible to verify the growth curves for some other bone dysplasiae presented in literature and predict dwarfism of the lower segment of the body in adulthood, e.g. in hypochondroplasia, metaphyseal chondrodysplasia of the type of Schmid, Turner syndromes, etc.