The prevalence of caries among 3-, 6-, 12- and 19-year-olds in Sweden was followed during the period 1985-1994 through county council reports to the National Board of Health and Welfare. Nearly all the county councils take part in this reporting, and the details for 1994 were based upon 74% of all the country's 12-year-olds and 81% of all the 19-year-olds. Particulars of caries are noted during the annual examination at national dental service clinics. Only manifest caries is recorded. For the age groups studied, the prevalence of caries diminished markedly during the period. The proportion of caries-free 3- and 6-year-olds increased. In 1994, 91% of the 3-year-olds and 64% of the 6-year-olds were free of caries in the deciduous dentition. DFT for 12-year-olds sank from 3.1 to 1.5 during 1985-1994. For 19-year-olds, DFT changed from 8.5 to 5.2, while the proportion of individuals who were caries-free on approximal surfaces increased from 36% to 58%. The change for DFS-a (carious or filled approximal surface) was from 3.4 in 1985 to 1.6 in 1994. These changes in the mean values were accompanied by changes in the frequency distribution of the values for DFT and DFS-a. The proportion of severely carious individuals decreased greatly during the 10-year period studied. At the same time, the differences in caries prevalence among the 26 county councils evened out.