 Many studies are done on children to show the prevalence of bruxism among different ages , reports of prevalence range from 8-31 in the general population, the prevalence of bruxism in Egyptian children is unknown. Several symptoms are commonly associated with bruxism, including hypersensitive teeth, aching jaw muscles, headaches, tooth wear, damage to dental restorations e.g. crowns and fillings and damage to teeth. However it may cause minimal symptoms, and therefore people may not be aware of the condition,so this study is important to determine the prevalence of bruxism of preschool Egyptian children 