Purpose: Although the concept of successful aging is used widely in the field of gerontology, there is no agreed-on standard or common underlying definition for measuring success in aging. Our recent survey of an elderly male population asked respondents to define "successful aging." This paper describes the themes that evolved from those definitions, explores interrelationships between the themes, and examines the association between characteristics of respondents and the themes provided in their definition. Design and Methods: The Manitoba Follow-up Study has followed a cohort of 3,983 World War II Royal Canadian Air Force male aircrew recruits since July 1, 1948. At a mean age of 78 years in 1996, the survivors were surveyed and asked, "What is your definition of successful aging?" and "Would you say you have aged successfully?" A content analysis identified themes emerging from their definitions. Results: The most frequent of the 20 component themes from the definitions of successful aging as provided by 30% of the 1,771 respondents related to "health and disease"; "physical," "mental," and "social activity" were more likely to be found in a definition including "interest," "having goals," "family," or "diet," and they were less likely to be mentioned with themes of "independence" or "health." Many of the themes reflect an individual's attitudes toward life and the aging process. Current life satisfaction, self-rated health, and limitation in activities of daily living were significantly associated with an increased likelihood of reporting specific themes in definitions. Implications: As health care professionals adapt to the changing demographic composition of society, it should be of interest to understand what successful aging might mean to the elderly males to whom they are attending.