This study was conducted to assess caries prevalence, dental fluorosis among primary school children and fluoride concentration in drinking water in Sana’a governorate (The capital of Yemen).A total number of examined students of 17599, (9623 boys and 7976 girls) with an age range of 6-12 years and mean age of (8.8 ± 1.8). Dental caries was assessed according to the WHO criteria using (dft and DMFT Index), while the enamel fluorosis was assessed using Dean’s Index (WHO, 1997). A total of 146 water samples analyzed for fluoride concentration using F ion selective electrode (ISE) showed that the fluoride concentration ranged from (0.131 ppm) to (13.1 ppm) in different areas of Sana’a governorate. The result showed that the overall prevalence of dental caries was (67.6%), while the dental fluorosis was (30.1%). The caries experience decrease gradually with increasing water fluoride level from (0 to 2 ppm) then increase by increasing water fluoride level (>2 ppm). The fluorosis prevalence increases steadily by increasing fluoride level in the drinking water.