BACKGROUND While fluoridation is the most effective preventive measure against dental caries, it increases the risk of tooth mottling or fluorosis. METHODS A total of 2,003 children aged 5 to 21 years were examined by a dentist following the recommendations of WHO and the standardized system of Möller and Poulsen, including X-ray investigation. The clinical aspects of fluorosis were classified on a 5-point scale. Data on the medical history, socioeconomic conditions, oral hygiene, carbohydrate ingestion and fluoride supplements of these patients were also collected. RESULTS The majority of the 2,003 children, 1687 (84.2%), had never received dietary fluoride supplements. Only 93 (4.64% of the total) of the 316 children who had taken fluoride, regularly ingested the recommended daily dose of 1.0 mg F-. This group had 43.2% fewer incidents of tooth decay, and came from the higher socioeconomic environment. Tooth mottling was 9.58 times more frequent in this group of correctly protected children. However, the clinical aspects of fluorosis were minor, with no esthetic damage. CONCLUSIONS These results suggest that the fluoride dosage regimen commonly proposed is effective against dental caries and does not need any change to reduce the risk of fluorosis.