OBJECTIVE: To examine whether functional ability at age 75 and age 80 is associated with oral health and use of dental services cross-sectionally and whether changes in functional ability from age 75 to age 80 are associated with oral health and regular use of dental services at age 80. DESIGN: The study included a random sample of 75-year-olds at baseline and a follow-up study 5 years later. The data are treated as two cross-sectional studies at age 75 and 80, respectively, and as a longitudinal study from age 75 to 80. SETTING: The western part of Copenhagen County. PARTICIPANTS: The two cross-sectional studies of 75- and 80-year-old people included 411 and 321 persons, respectively. The longitudinal study from age 75 to 80 included the 326 persons who participated in both surveys. MEASUREMENTS: Oral health status was measured roughly by number of teeth and chewing ability. Use of dental services was measured by frequency of visits to a dentist or denturist. Functional ability was measured by two scales on mobility in relation to tiredness and need of help. Changes in mobility from age 75 to 80 is described as (1) improved or sustained good, (2) decreased, and (3) sustained poor. Gender, chronic diseases, self-rated health, socio-demographic factors, living alone, and social relations were included as possible confounders. RESULTS: The odds ratio of having no or few teeth was 1.7 (1.1-2.6) in 75-year-old individuals who felt tired in mobility, 1.7 (1.0-2.9) in 80-year-old persons who needed help with mobility, and 2.7 (0.94-7.5) in persons with sustained need of help with mobility from age 75 to 80. The odds ratio of chewing difficulties was 1.7 (1.1-2.8) in 80-year-old people in need of help, and 1.8 (1.1-3.0) in persons age 75 to 80 needing sustained help. Dentate 80-year-old persons who felt tired in mobility had an odds ratio of 2.0 (0.94-4.2) of not using dental services. CONCLUSIONS: The results indicate that oral impairment (e.g., having no or few teeth), oral functional limitations (e.g., chewing problems), and general functional limitations (e.g., mobility problems) are interrelated and that prevention of disabilities should be aimed at both functional limitations and oral health problems if the intention is to promote a good life in old age. In addition, the results point to the importance of taking problems in mobility seriously in delivering preventive services to old people because people who are tired or dependent on help seem to be at a higher risk of not using dental services regularly.