The investigation focused on longitudinal changes of oral health in a group of adults with intellectual disability. A number of 124 individuals, aged 21-40 yr in 1990, were followed during 8.5 yr. The incidence and prevalence of caries, incidence of tooth mortality, and interproximal bone loss were registered from clinical examinations and bite-wing radiographs. The subjects visited the dental clinic for preventive dental care on average every third month during the period. The caries incidence was low, on average 0.51 new lesions per yr. Persons with mild intellectual disability experienced more caries than other subjects. During the 8.5 yr, the subjects had lost on average 1.82 teeth, with periodontitis dominating as the reason for tooth mortality. Individuals who cooperated poorly with dental treatment had lost the most teeth. The average annual bone loss in all subjects was 0.03 mm. Subjects with Down syndrome had a higher bone loss compared to those with other diagnoses of intellectual disability. Thus, the major part of the persons with intellectual disability showed satisfactory oral health. However, subjects with poor ability to cooperate with dental treatment and subjects with Down syndrome showed an increased risk for impaired oral health.