OBJECTIVE To determine the prevalence and severity of dental caries and to assess treatment needs among schoolchildren aged 6 and 12 in Blumenau, Brazil, and to compare the results found for private and public schools. METHODS A schoolchildren population of Blumenau, SC, Brazil, was studied. A random sample of 1,473 schoolchildren from Blumenau, Brazil, was obtained. Four strata were studied: 6 and 12 years old schoolchildren attending public and private schools. WHO (1997) criteria for caries diagnosis and treatment needs were used. RESULTS The prevalence of caries in the primary dentition of 6-years-old children was 60.9% and 34.9% in public and private schools (p<0.0001), respectively. The mean DMF-T for children aged 6 was 2.98 and 1.32 for public and private schools, respectively, (p<0.0001), and 2.42 for the whole sample. The prevalence of caries in the permanent dentition of 12-years-old children was 54.7% and the mean DMF-T was 1.46 for public schools. The response rate for private schools was low and the results could not be analyzed. Forty-two percent and 77.0% of children aged six of public and private schools, respectively, had no treatment needs. For those aged 12, the percentage was 53.0% for public schools. CONCLUSIONS The prevalence of caries and the treatment needs among schoolchildren in Blumenau was low, but there was a statistically significant higher prevalence and higher severity in public school children aged six. The prevalence of caries and treatment needs at the age of 12 in public schools were also low.