This paper reports the effect of chronic high fluoride exposure on children’s intelligence quotient (IQ). In this cross sectional study, two urban communities with similar socio-economic and cultural status but with different levels of fluoride in drinking water, in Kerman province of Iran were studied: Koohbanan City (fluoride 2.38 mg/L), Baft City (fluoride 0.41 mg/L). Study samples consisted of 119 children 6 to 9 years old: 50 children from Koohbanan and 60 children from Baft. Raven’s progressive matrices used to determine the effect of fluoride exposures on children’s IQ. The statistical analysis was carried out using the t-test, the chi-square test and the Mann-Whiteney test. In the low fluoride area (control group), the mean IQ score of children was 97.80±15.95 that decreased to 91.37±15.63 for the high fluoride group (Koohbanan’s children), it was significantly different from the control group (P<0.05). Although fluoride is widely promoted for prevention of dental caries, its overconsumption may lead to dental fluorosis and other adverse effects. Based on the findings, the chronic exposure to high levels of fluoride can be one of the factors that influence intellectual development. Therefore, it is necessary to think about some solutions for preventing the bad effects of excessive intake of fluoride ion to the body, especially in cities like Koohbanan.