The purpose of this research was to determine the fluoride concentration in drinking water of Mianeh city in the province of East Azerbaijan, Iran. This crosssectional research was carried out on all 14 groundwater sources of drinking water in 2008. The results show that the mean fluoride concentration in spring, summer, autumn, and winter was 0.295±0.039, 0.47±0.17, 0.48±0.18, and 0.4±0.06 mg/L, respectively. Moreover, the concentration of fluoride in all water sources was below the permissible concentration based on Iran drinking water standards, but it was in standard range proposed by WHO. In addition, the DMFT index of the children between 6 and 9 years old in Mianeh was higher than the Iran DMFT index
