Caries and costs: an evaluation of a school-based fluoride varnish programme for adolescents in a Swedish region E-K. Bergström, P. Lingström, M. Hakeberg, L. Gahnberg and U.M. Sköld In 2003, 19 public dental clinics in Västra Götaland Region implemented a population-based programme with fluoride varnish applications at school every six months, for all 12 to 15 year olds. In 2008, the programme was extended to include all 112 clinics in the region. Objective: To evaluate caries increment and to perform a cost analysis of the programme. Basic research design: A retrospective design with caries data for two birth cohorts extracted from dental records. Three groups of adolescents were compared. For Group 1 (n=3,132), born in 1993, the fluoride varnish programme started in 2003 and Group 2 (n=13,490), also born in 1993, had no fluoride varnish programme at school. These groups were compared with Group 3 (n=11,321), born in 1998, when the programme was implemented for all individuals. The total cost of the four-year programme was estimated at 400SEK (≈44€) per adolescent. Key words: adolescent, caries prevalence, dental caries, fluoride varnish, prevention, school based prevention