OBJECTIVES: To examine whether tooth loss at age 70 is associated with onset of disability at 5-, 10-, 15-, and 20-year follow-up and to mortality at 21-year follow-up. SETTING: Community-based population in Copenhagen. DESIGN: A baseline study of a random sample of 70-year-old people born in 1914 and follow-up 5, 10, 15, and 20 years later. PARTICIPANTS: A total of 573 nondisabled individuals participated in the study of 70-year-olds in 1984, 460 participated in the 5-year follow-up, 292 in the 10-year follow-up, 150 in the 15-year follow-up, and 78 in the 20-year follow-up. MEASUREMENTS: Data from interviews and a medical and oral examination. Oral health was measured according to number of teeth (0, 1-9, 10-19, > or = 20). Disability was measured using the Avlund Mob-H scale at age 75, 80, 85, and 90. Mortality data were obtained from the National Death Register. RESULTS: Being edentulous or having one to nine teeth was associated with onset of disability at age 75 and 80. Health-related variables and education attenuated the associations between edentulism and onset of disability, although they remained marginally significant, whereas the association between having one to nine teeth and onset of disability remained unchanged and statistically significant at 10-year follow-up (odds ratio=3.02, 95% confidence interval (CI)=1.26-7.24). Persons who were edentulous at age 70 were at significantly higher risk of mortality 21 years later, also in the adjusted analysis (hazard ratio=1.26, 95% CI=1.03-1.55). CONCLUSION: Tooth loss is independently associated with onset of disability and mortality in old age. The findings indicate that tooth loss may be an early indicator of accelerated aging.