This study was conducted to get normative data of crown diameter of primary teeth of Yemenis children among primary schools students (3-7 years old) in capital of Yemen; Sana’a city Twenty one governmental schools were included.This cross-sectional study was carried out on 1000 children, divided according to gender into 2 groups; 500 students were boys group, while 500 students were girls group.In order to reach to our target morphologically sound sample we were excluded any subject that not fulfilled our predetermined criteria but we recorded those subject with dental caries and enamel defects and represented statistically. Finally, we found only 113 boys and 104 girls with sound primary teeth .We were selected only (100 male and 100 female) for Odontometric measurement’s.Data were collected through a work sheet the crown dimensions were recorded mesiodistally, buccolingually and crown height.Concerning dental caries and enamel defects that were excluded from odontometric study:- 315 males (63%) and 329 females (65.8%) were found to have Dental caries.- 142 males (28.4%) and 129 females (25.8%) were found to have Enamel hypoplasia.- 113 males (22.6%) and 104 females (20.8%) were sound morphologically.Regarding the Odontometric measurments:A special device was designed with a platform on which the cast to be placed and fixed with screws that facilitate the standardization of measurements.All measurements were taken using digital caliper (Mitutoyo, Japan), with accuracy (0.01 mm).In this study, the average of mesiodistal and buccolingual sizes and the heights of all primary teeth of Yemeni children were obtained.Concerning the comparing between the published data of Arab population and the result of our present study:- The Egyptian and Jordanian population, When comparing the mesiodistal crown size obtained in the present study with those reported by other authors, no specific pattern was observed. The present values were numerically greater than, but close to the values obtained by (EL-Nofely et al, 1989) in Egyptian children, where all deciduous teeth were also evaluated.- The study of Jordanian population (Hattab FN et al,1997) that revealed largest mesiodistal value in comparison to the Egyptian and our study of Yemeni children.