Abstract： Objective To investigate the prevalence and distribution characteristics of dental fluorosis of children aged 8 - 12 in Wushan and Fengjie counties of Chongqing and to provide a scientific basis for prevention and control of the disease.Methods Twenty townships(towns) in Fengjie county and 18 in Wushan county were selected as survey points by random cluster sampling in 2010.Dental fluorosis of all the children aged 8 - 12 was examined with Dean index.The detection rate of children's dental fluorosis,defect rate and dental fluorosis index were compared between the two counties.Results Totally 38 209 children aged 8 - 12 were investigated.The total detection rate of dental fluorosis was 43.09％( 16 466/38 209) in the two counties.The detection rates of dental fluorosis in Wushan and Fengjie were 48.98％ (9397/19 186)and 37.16％(7069/19 023),respectively,and the difference was statistically significant(x2 =544.03,P ＜ 0.01 ).Total detection rates of dental fluorosis of the five age groups(8,9,10,11,and 12-year-old age groups) were 32.52％(2157/6632),40.07％(2672/6668),43.67％(3420/7831 ),46.01％ (3861/8391) and 50.14％ (4356/8687),respectively,and the difference was statistically significant (x2 =510.50,P ＜ 0.01),Dental fluorosis indexes in Wushan and Fengjie were 0.713 and 0.485,respectively.Defect rates of dental fluorosis in Wushan and Fengjie were 4.05％ (777/19 186) and 1.57％(298/19 023),respectively.Conclusions The total detection rate of dental fluorosis of the two counties is still high,which gradually increases with age.Wushan is still an endemic area of dental fluorosis,and Fengjie is at the edge of the