Purpose: Using the ICDAS (International Caries Detection and Assessment System), to assess caries experience in the primary dentition of preschool children living in a socioeconomically poor area with a nonfluoridated water supply, and to compare the stages of caries manifestation between children from private and public schools. Materials and Methods: This census included all children aged 3 to 5 years from public and private schools from Teixeira, Brazil. Clinical examinations were carried out by two calibrated examiners using ICDAS, the results of which were converted into components of dmf-s and dmf-t. Results: The majority of children had caries; the prevalence of enamel and dentin lesions was 81.7%. The prevalence of dentin lesions alone was 62.1%. The mean values of the d2mf2-s/d2mf2-t indices (enamel and dentin lesions) and d3mf3-s/d3mf3-t indices (dentin lesions) were 13.5 ± 14.9/6.8 ± 5.8 and 7.4 ± 10.9/3.0 ± 3.6, respectively. There was no significant difference between the dmf-s/dmf-t indices of children from private vs public schools (p > 0.05). Conclusion: Caries was highly prevalent in the primary dentition of this Brazilian population, and the presence of noncavitated lesions was the most prevalent condition. Children from private and public schools showed similar caries experience. Keywords: dental caries, ICDAS, oral health, preschool children, primary teeth