In order to evaluate trends in caries experience, a 20% random sample of 12-yr-old residents of Reykjavik, Iceland (252 children) was examined clinically and radiographically in 1991 under conditions consistent with those of the survey conducted in 1984. In addition to caries data, frequency of toothbrushing and use of fluoride dentifrice were recorded. The mean DFT and DFS were 3.0 and 4.1, respectively. The decrease in caries experience reached 60% with an annual fall in DFS of nearly 10%. During the 7-yr period between examinations the decline in DFT and DFS scores averaged 5.2 and 8, respectively, the annual reduction amounting to 0.7 DF teeth or 1.1 DF surfaces per child. The ratio of approximal/occlusal caries and the proportion of approximal caries were similar in both surveys. Fourteen percent of the children were free from manifest caries in 1991, but only 2% in 1984. Polarization between low and high prevalence individuals had intensified. Ninety-five percent of the children brushed their teeth regularly and 97% reported using a fluoride dentifrice.