The aim of this study is to investigate the maxillary midline diastema in Saudi schoolchildren in Riyadh; particularly prevalence and some likely related etiological factors with regard to gender and age. The present epidemiologic study was undertaken in intermediate schools of Riyadh City. A total of 1,825 Saudi schoolchildren (1007 boys and 818 girls) aged 12 to 16 years were randomly selected. Clinical examination was carried out in the schools within the students' classrooms by two experienced examiners using simple plain mouth mirror, small light source and stainless steel ruler. Students with a history of orthodontic treatment or prosthodontic restorations in the upper anterior teeth and periodontal disease were not included in the sample. An especially composed chart was used to record demographic data
and inter arch parameters. All data were analyzed using SPSS program and simple descriptive statistics with regard to boys and girls. Results revealed the prevalence of maxillary midline diastema was 394 (22%) out of 1825 students examined. A similar figure, though slightly greater prevalence of maxillary midline diastema in boys (22%) than in girls (21%). The highest prevalence was observed in 13 years age group (7.7%). The width of maxillary  midline diastema ranged between 1-2 millimeters demonstrated (79.2%) of total sample, greater in boys (91%) than girls (64.4%), and (100%) in 16 years age group. The maxillary midline diastema width of 3-4 millimeters occurred more in girls (35%) than boys (9%), and in 12 years age group (35.5%) than other age groups with decrease up to 16 years of age. Among the observed etiological factors in both sexes and different age groups, spacing in anterior region (35.5%) was the most frequent etiological factor associated with maxillary midline diastema. Followed by increased ovejet (15.7%), missing tooth (11%), while the frequency of deep bite and anterior open bite was 6.3% and 5.8% respectively. It was concluded that maxillary midline diastema is a common occurrence in Saudi children associated with multifactorial etiology. Consideration of etiological factors and individual treatment planning are essential in the proper management of maxillary midline diastema.