The Saskatchewan Health Dental Plan (SHDP) is a publicly funded dental insurance program for children between the ages of five and 16 years residing in the province. In 1981, fissure sealants were added as a covered expense. Until September 1, 1987, sealants and other dental treatments covered under the SHDP were provided to schoolchildren by dental therapists in dental clinics established in elementary schools throughout the province. After September 1, 1987, the provision of dental services was transferred to private practitioners in the province. The objectives of this study were to (1) estimate the retention rates of sealants after one, two, and three years of placement; and (2) conduct a longitudinal followup of sealed and unsealed sound teeth to measure the effectiveness of sealants in reducing dental caries incidence. Relative to the first objective, a cohort of children was identified and comparisons were carried out for the periods of 1982-83, 1982-84, and 1982-85. For the last objective, a longitudinal evaluation of effectiveness was carried out only for children five to seven years of age in 1981. Saskatchewan children, who experienced higher caries prevalence than children in the United States, had the highest caries increments on occlusal surfaces of posterior teeth. About 79 percent of the sealants applied by dental therapists were retained three years after application. Sealed teeth experienced 46 percent less caries than unsealed teeth four years after the application of sealants.(ABSTRACT TRUNCATED AT 250 WORDS)