After the definition of dysglossia, information is given about epidemiology, symptomatic profile, aetiology and pathogenesis of this disease. The nomenclature of velopharyngeal insufficiency is discussed, and its symptomatic profile is presented in detail. After explaining the structure of the velopharyngeal valve, different general categories of velopharyngeal closure, anatomical structures and physiological components are explicated. Clinical knowledge is imparted on submucous cleft palate and occult submucous cleft palate, the correlation of lymphoid tissue and resonance disorders and hyponasality and velopharyngeal insufficiency. Fundamental information is given about genetics. After an explanation of the evolution and development of the head and face, syndromes with hypernasal speech as a possible feature are presented. Genetic counselling and future directions in genetics are introduced.