Despite the reduction in the prevalence of dental caries, very little is known about the prevalence of the disease, especially in deciduous teeth, in small Brazilian cities (<20,000 inhabitants). The aim of this study was to evaluate the prevalence of dental caries in children aged 3 and 5 years of age in the city of Cambira - State of Parana. All children that participated in the national vaccination campaign against poliomyelitis in 2002 at the two basic health units of the city were examined. The campaign covered 99.5% of the population aged 1 to 5 years. Two previously trained and calibrated dentists performed the clinical examinations after the children brushed their teeth and recorded their caries experience by means of the dmf index. The results showed that there was no statistically significant difference in the prevalence of the disease between the male and female genders and between the rural and urban zones. At the age of 3, 68.50% of the children were caries-free, compared to 31.10% at the age of 5. In the total population, 11.19% of the children accounted for 50.86% of the teeth affected by dental caries. The dmf index at 3 and 5 years in the study population was 2.10 and 3.51, respectively. These data showed that the city has not yet reached the goals proposed by the WHO for the year 2000, what indicates the need for greater investment in programs aimed to prevention and control of the disease.