Abstract: The aim of this study was to determine DMFT index (Decayed, Missing and Filled Teeth) in the 12 years old students in Behshar city and to determine the fluoride concentration in drinking water Sources. The survey was performed using the cross-sectional method on 300 students’ selected using multi-stage sampling . The DMFT index of permanent teeth was determined, using its standard methods recommended by world Health organization. The water fluoride level was estimated in water supplies, using SPANDS method. The Annual Mean Maximum Temperature (AAMT) recorded during the last two yeas were Collected from the meteorological Center. A total number of 300 students (50% boys and 50% girls) aged 12 years and 120 water samples were assessed. The results showed that mean fluoride concentration of drinking water during one year was 0.25 ppm, which Less than normal level. The average AMMT of behshar city is 22±4°C at which the optimal fluoride in drinking water of Behshar using Galagan and Vermillion equation was calculated to be 0.8 ppm. The mean DMFT value was 1.48±0.13 and was higher in girls in comparison with boys. Results indicate that the availability of other sources of fluoride must also be considered and taken into account in the planning of programs in public health dentistry.