Significance: Although physical activity is linked to healthy longevity, few older adults exercise on a regular basis. Furthermore, there is a dearth of knowledge about older adults’ motivations toward exercise participation, and how motivation differs across stages of physical activity behavior change in this segment of the population. In part, this is due to the lack of measurement scales that assess motivation toward moderate physical activity in both exercising and non-exercising older adults. This project adapted a psychometrically valid motivation scale, the Exercise Motivation Inventory – Revised (EMI-2: Ingledew et al., 1998; Markland & Ingledew, 1997) to an older adult general population sample. The EMI-2 has been used in younger samples to assesses intrinsic and extrinsic motivation constructs based on self-determination theory (Deci & Ryan, 1985). Self-determination theory provides a unique framework to study the multifaceted dimensions of exercise motivation, and it is particularly applicable to older adults as aging sometimes involves perceptions of decreased autonomy and competence. Design: 645 older adults (M age: 63.8/sd: 8.3) completed self-administered questionnaires that included 44 items of the EMI-2 during outpatient visits to their primary care physicians. Physical activity was defined as moderate activity, including walking and gardening. Principal components analyses of collected data including orthogonal rotation by the Varimax with Kaiser normalization procedure, and the elimination of 7 items in order to yield a factor structure that reflected gender invariance. Results: Results yielded six factors/subscales consisting of 37 items with eigenvalues greater than 1.0, accounting for 70.3% of the total variance. The six factor/subscales assess intrinsic motivation (Enjoyment subscale), self-determined extrinsic motivation (Health & Fitness, Social/Emotional Benefits, and Stress Management subscales), and nonself-determined extrinsic motivation (Weight Management, and Appearance subscales). Internal consistency is excellent, with reliability coefficients ranging from .86 to .94. Factorial invariance across gender was also demonstrated. Overall findings indicate that the EMI-2 is an appropriate tool to assess extrinsic and intrinsic motivation toward moderate exercise participation in currently exercising and non-exercising older adults if the revised subscale structure that was yielded from this study is used in the analysis of results. The utilization of the EMI-2 in this manner can contribute to understanding older adult physical activity motivation at all levels of engagement, and ultimately to the development of efficacious interventions to increase and sustain exercise behavior in this population.Keyword(s): older adult/aging issues, physical activity, research