Knowledge of dental eruption pattern must be taken into consideration during occlusal development, malocclusion diagnosis and efficient treatment planning.Aim of the study: Determine the eruption dates and sequence of primary and permanent teeth and Correlate between chronological and developmental age of eruption of primary and permanent teeth in a group of children in Giza Governorate, Egypt represented by percentage of deviation from the standard range.Study Design: Cross sectional observational study.Subjects and Methods: The study sample consisted of 1656 healthy Egyptian children of both sexes, 1120 children were randomly selected from Giza governmental schools. And 536 children were randomly selected from children attending Maternal and child welfare centers and Giza public hospitals. Children were selected according to certain criteria then examined and the status of the eruption of each primary & permanent tooth was recorded on a specially designed survey sheet