Background & objectives: Dental caries is one of the most chronic diseases in children. Various factors were effective in incidence andprevalence of dental caries. The aim of this study was to determine the dental caries prevalence among 6-12 yearsold school children in Ardabil city.

  Methods : In this descriptive–cross sectional study a total of 847 school children (444 girls and 403 boys) were randomly selected from public and private schools in all over of Ardabil city.Clinical examination of children have been done for dental caries according to world health organization (WHO) criteria including determination of DMFT, dmft, DMFS and dental caries prevalence. Data were analysedin SPSS.16 by statistical methods.

  Results: Total prevalence of dental caries was 79.7% in children with 71.1 % in permanent and 88.3 % in primary dentition. The mean of dmft, DMFT, DMFS indexes were 2.74± 0.09, 1.6±0.1, and 3.5± 0.1, repectively.Results showed that there was a significant relation between DMFT, dmft and DMFS and age group.

  Conclusion : Results showed that the dental caries prevalence among 6-12 years-old school children in Ardabil city was higher than the world standard. Therefore, improving the existing dental services, programing and performing education, prevention and treatment programs for oral health between school children seems tobe necessary in the future.