OBJECTIVES: The Icelandic Oral Health Survey aimed to obtain new national data on the oral health of Icelandic children and teenagers. METHODS: A representative stratified random cluster sample of 2251 Icelandic children in first, seventh and 10th grade, aged approximately 6-, 12- and 15-years old was examined for caries prevalence using the ICDAS criteria. Bite-wing digital radiographs were obtained for the children in 7th and 10th grade. RESULTS: D(3)MFT scores by visual examination of 6-, 12- and 15-year olds were 0.12, 1.43 and 2.78 respectively but when including radiographs, the D(3)MFT rose to 2.11 at 12 years and 4.25 at 15 years. The Significant Caries Index, SiC, by visual examination for 12 and 15 y was 3.7 and 6.7 respectively but was 4.7 for 12 y and 8.9 for 15 y with radiographs. In all age groups and at most disease levels, caries was active in the majority of the lesions (58-100%). The percentage of children with no visually detectable caries at D(3)/D(1) level was 93%/74% for 6 years, 48%/22% for 12 years and 35%/16% for 15 years. When radiographs were included the percentage reduced to 34%/15% for 12 years and 20%/6% for 15 years. Approximately 80% of 12- and 15-year-olds had at least one of their first molars sealed, with the mean number of sealed first molars being 2.2 among 12 y and 2.0 among 15 y. CONCLUSIONS: Caries levels were higher than expected in this national survey and further away from the goals of the National Health Plan for 2010 than anticipated. Caries distribution was skewed with more than half of the children having low caries scores but a wide distribution of caries experience was seen among the remaining population.