The concept of "successful aging" has become widely accepted in gerontology, yet continues to have no common underlying definition. Researchers have increasingly looked to older individuals for their lay definitions of successful aging. The present analysis is based on responses to five questionnaires administered to surviving participants of the male Manitoba Follow-up Study cohort (www.mfus.ca) in 1996, 2000, 2002, 2004, and 2006 (n = 2,043 men were alive at a mean age of 78 years in 1996). One question on each survey asked: "What is YOUR definition of successful aging?" Applying content analysis to the 5,898 narratives received over the 11 years, we developed a coding system encompassing 21 main themes and 86 sub-themes defining successful aging. We quantitatively analyzed trends in prevalence of themes of successful aging prospectively over time. Our findings empirically support colleagues' past suggestions to shift from defining successful aging in primarily biomedical terms, by taking lay views into account. (Contains 2 tables and 1 figure.)