Changes in the distribution of caries in economically developed nations over the last 15-20 years include 1) an overall decline in prevalence and severity in child populations; 2) an increasingly skewed distribution, with most disease now found in a small number of children; and 3) concentration of caries in pit and fissure lesions. Exposure to fluoride is usually seen as the principal reason for the caries decline, with little change in intraoral levels of cariogenic organisms or the annual consumption of sugars. Prevention activities are still most often conducted under policies that were established at a time when caries was a more widespread public health problem, so these policies should be critically examined in the light of modern conditions. While prevention should remain the prime activity of public health agencies, despite the reduced severity of caries, the relative economic efficiency of various procedures should be constantly evaluated. Despite the attractions of targeting, cost-effective prevention should be aimed first at the whole population, with more expensive activities targeted to all children in a chosen geographic area rather than to individually selected children. In the Scandinavian countries the prime population strategies are the regular use of fluoride toothpaste and public education that emphasizes oral hygiene. In selected areas where caries levels are still relatively high (that is, targeted geographic areas), fluoride rinse and tablet programs, provided for a whole classroom at a time, can enhance intraoral fluoride levels where necessary. Fluoride varnish and sealants, though effective, are expensive and need careful selection of locality and teeth to be efficient. Individual children with a persistent caries problem, now relatively small in number, can receive individualized preventive treatment in the clinics of the school dental service.