The purpose of this study is to measure the long-term effects of a combination of self-applied fluoride methods among schoolchildren living in a rural area with low concentrations of fluoride in drinking water. Participating children rinse weekly with a 0.2% sodium fluoride solution and ingest daily a 1-mg fluoride tablet in school under supervision of their teachers, and received fluoride toothpaste and toothbrushes for use at home. In 1980, dental examinations of children ages 6-14, who had continuously participated in the program for 1 to 8 years, depending on their school grade, had an overall mean caries prevalence of 3.22 DMFS, 49% lower than the corresponding mean score of 6.31 DMFS for children of the same ages at the baseline examination. The preventive program inhibited decay in all types of tooth surfaces: 37% in occlusal, 41% in buccolingual, and a striking 86% in mesiodistal. At each succeeding follow-up survey, benefits have continued to improve; the reductions in caries prevalence were 18% after 2 years, 35% after 4 years, 45% after 6 years, and 49% after 8 years. Findings in approximal tooth surfaces have also continued to improve as the length of the program has increased; reductions in caries in mesiodistal surfaces were 32%, 69%, 85%, and 86% after 2,4,6, and 8 years, respectively. Internal analyses of data indicate that the decline in dental caries prevalence resulted from the fluoride program and not from an unexplained natural decline in caries prevalence. The self-applied combined fluoride regimen used in this program has been shown to produce a pronounced anticaries effect.