In cross-sectional studies conducted in 1967, 1971, 1976, 1980, 1987, 1992, 1997 and 2002, 4-year-old children in Umeå, a city in northern Sweden, were examined for dental caries and background factors such as oral hygiene habits, use of fluorides, and sugar consumption. The same methods and criteria have been used in each of the studies from 1967 to 2002. The number of children with caries had declined from 87% in 1967 to 42% in 1987, but then the decline levelled out. In 2002, 46% of the children had caries with a mean dmfs value of 2.0 +/- 3.6. Six percent of the children had 10 or more dmfs. Immigrant children had a higher caries prevalence (p < 0.01). A significant difference in the dmfs values was found in children according to tooth-brushing frequency (p < 0.01). Although the consumption of sugary products between meals increased between 1987 and 1997, no changes were noted from 1997 to 2002. In conclusion, no important changes in caries prevalence have taken place during the last 15 years. The frequency of tooth-brushing and immigrant background had a significant association with caries prevalence.