Cleft lips and palates (isolated or complete) arise from disorders in embryonic development. Only the lip, the jaw and the lip as well as the lip, jaw and palate may be affected (rarely the palate alone). Endogenous (hereditary) and exogenous factors (e.g., viral infections during pregnancy, drugs, lack of vitamins and oxygen) may be the cause for cleft formation. They can be distinguished into one-sided and two-sided cleft formations. Treatment of cleft lips and palates usually requires the cooperation of maxillofacial surgery and orthodontal measures and is usually performed in specialised facilities (specialist clinics, university clinics).