The developmental anomalies of dental hard tissues are relatively common in children. These anomalies can involve separately the enamel and they are due to many factors acting during odontogenesis. The paper deals with the main ethological factors and describes a case of idiopathic hypercalcemia. It is normally accompanied by aortic stenosis, mental retardation and a characteristic elfin face. This is called Williams syndrome. In this case we only found enamel hypoplasia on the cusps of the first molars.