This paper describes a new measure of Active Life Expectancy, called Active Life Classification (ALC) in which the criterion for successful aging is a combination of good functional ability and high social participation. OBJECTIVES: 1) to describe the distribution of ALC among 75-year-old men and women, 2) to investigate the association between ALC and life satisfaction and 3) to describe how ALC is determined by socio-demographic, psycho-social, and health factors. DESIGN: A cross-sectional population survey. SETTING: Eleven municipalities in the Western part of Copenhagen County in 1989. SUBJECTS: A random sample of 75-year-old people who were invited to participate in the study (participation rate: 89, n = 477). MAIN OUTCOME MEASURE: ALC is a combination of two dichotomized variables: functional ability (dependent vs not dependent of help) and social participation (low vs. high). RESULTS: For both men and women an active life (measured by ALC) was significantly associated with life satisfaction. For men only good self-rated health was related to ALC in the multivariate analysis. Among women high income, many social contacts, good self-rated health, good memory and lack of chronic diseases were associated with ALC. CONCLUSIONS: It is an advantage to combine functional ability and social participation in the description of quality of life in old age, as 1) a high social participation may compensate for a poor functional ability, and vice versa, 2) the combined measure is meaningful for both sexes, and 3) it gives more information than the two concepts used as separate outcome measures.