ABSTRACTIn the absence of a universally agreed-upon definition of successful aging, researchers increasingly look to older adults for layperson views of aging and definitions of successful aging. To use lay definitions in studies of aging, however, researchers must address the definitions' consistency. In 2004, surviving members of the Manitoba Follow-up Study male cohort (mean age: 83 years) were asked twice for their definition of successful aging. A consistency category was assigned based on the similarity of themes in each of 654 pairs of definitions. At least half of the main themes were similar in 70 per cent of the definition pairs; 80 per cent of respondents repeated at least one theme. Positive or negative health events in the four-week interval between definitions and specific respondents' characteristics did not vary across consistency categories. This evidence for consistency supports our continued reliance on lay definitions of successful aging.