Background and purpose: Fluoride is one of the drinking water contaminants regulated by EPA. This ion, in low doses in the mouth reduces tooth decay without health risk and at much higher doses causes health complications and can be toxic. The major sources of exposure to fluoride are drinking water, food, dental products, and pesticides. The biggest contributor to exposure for most people in Iran is drinking water. This study was carried out to determine groundwater fluoride concentration of Hamadan province located in the west of Iran in 2012. Materials and Methods: Ground water samples were collected from 192 sampling point, during dry and wet seasons. Fluoride concentration was determined in the water samples using UV-Spectrophotometry method (DR 5000) and SPADNS Fluoride Reagent Solution. Results: The fluoride concentration of ground water of examined regions varied between 0 to 1.78 mg/l. Mean concentration of fluoride samples and standard deviation were 0.574 and 0.351 mg/l respectively. The results showed that 49% of fluoride concentration samples were less than the standard value according to National standards of IRAN and WHO guideline. Conclusion: According to low level of fluoride concentration in this province, fluoride supplements such as mouth washes, consumption of fluoride containing foods and water fluoridation are recommended to reduce caries development.