For many years the children of Guam have experienced a high prevalence of dental caries. Surveys conducted on the fluoride-deficient island found that caries levels were double those of US mainland children. In 1976 a school-based fluoride mouthrinse program was initiated involving over 22,000 children in grades kindergarten through eight in weekly rinses with 0.2% neutral NaF. A clinic-based dental pit and fissure sealant program was added in 1984 to the fluoride mouthrinse program. Over 15,000 children participated annually in the sealant program where more than 75,000 teeth were sealed the first year. After 8 yr of fluoride mouthrinsing (1976-1984) mean DMFS scores were 1.79 surfaces per child lower compared to baseline, a decrease of 0.22 DMFS per child per year. During this period proximal DMFS scores decreased 61%, buccal-lingual surfaces 31%, and occlusal surfaces 7%. After 2 yr of fluoride mouthrinsing and sealant application combined overall DMFS scores decreased an additional 2.34 surfaces per child, a reduction of 1.17 DMFS per child per year. Most of this decline took place on pit and fissure surfaces. For the 10-yr period a reduction of 4.13 DMFS per child was seen--a decline from 7.06 DMF at baseline to 2.93 DMF surfaces per child in 1986. This long-term evaluation indicates that dental sealants when used in combination with fluoride mouthrinse were particularly effective in lowering the prevalence of dental caries. Schoolchildren in participating grades on Guam now have dental caries rates close to those of US schoolchildren.