Developmental defects of enamel remain as a permanent record of a disturbance during amelogenesis. They may present in different forms, some of which may be perceived by an individual as being disfiguring and so requiring treatment to improve the appearance of the teeth. The aim of this review is to address the aetiological factors for DDE because the knowledge is essential for clinicians when explaining and discussing the presence of DDE with patients and their parents. The possible aetiological factors for enamel defects in permanent teeth can be broadly divided into two main categories: those with a localized distribution and those with a generalized distribution. Amongst the causative agents of localized defects of enamel are trauma, localized infection and irradiation. Amongst the causative agents of generalized defects of enamel are genetic disorders and systemic disturbances including intoxications, perinatal and postnatal problems, malnutrition, infectious diseases and a range of other medical conditions. Most of the available data on the aetiology of enamel defects have been gained from animal studies and case reports of children with systemic disorders. The lack of robust data makes the results of these studies inconclusive.published_or_final_versio