The authors describe abnormalities in the development of the cranium and soft tissues of the face in different types of facial clefts, their origin, consequences and importance for treatment. The basic abnormalities from which the majority of others can be derived are a reduced length of the maxilla, narrowing of the dentoalveolar arch and dentoalveolar retroinclination, which are of postoperative origin, and a lower height of the upper jaw, a posteroposition of the maxilla and shorter ramus as well as body of the mandible which are of prenatal origin. By orthodontic treatment only the dentoalveolar retroinclination and narrowing of the dental arch can be influenced. The most serious abnormality is a reduced length of the maxilla, associated with retrusion, impaired sagittal intermaxillary relations and anterior cross bite, or possibly reduction of the mandibular length associated with posteriorotation and impaired vertical intermaxillary relations. In the soft tissues the basic abnormalities are a reduced length and thickness of the upper lip, a broader nose, narrowing of the oral slot (clinically insignificant) and asymmetry of the oronasal region. Deviations are of varying extent and proportion in different types of clefts and differ as to the impact on the patient and his treatment.

        Key words: clefts of the lip and palate – configuration of the face – basic abnormalities – origin and impact of abnormalities