This review addresses two major issues related to the use of pit and fissure sealants. First, the epidemiology of occlusal caries for children and adults is examined to determine if there is a basis for administering sealant programs to different age groups. Second, the effectiveness of pit and fissure sealants in fluoridated and non-fluoridated communities is compared. Changes in effectiveness of sealant over time are evaluated in terms of percent effectiveness, complete retention, caries incidence, and reapplication rates. Based on epidemiologic evidence, sealant programs can be justified for children and young adults, but not for older age groups. Based on the literature reviewed, following one application of autopolymerized or visible-light-cured sealant, the median percent effectiveness declines from 83 percent after one year to 55 percent after seven years. Similarly, the median complete retention declines from 92 percent after one year to 66 percent after seven years. Conversely, the median percent of sealed first molars becoming carious and/or restored increases from 4 percent after one year to 31 percent after seven years. Large differences in sealant effectiveness are not apparent between studies performed in fluoridated and fluoride-deficient communities.