A routine investigation of 270 preschool children revealed a high incidence of malocclusion, frequently associated with clinically discovered disturbances of mandibular movement, temporomandibular joint functions, habits or defective speech articulation. The prevalence of malocclusion and of functional disturbances in the deciduous dentition demands not only for a more intensive prevention of dental caries but a careful attention to early functional disturbances in occlusion, in mandibular movement and other numerous functions.