Even though the physiological, psychological, and social benefits of physical activity are well documented, few individuals sufficiently engage in it. Older adults are the least active segment of the population, despite evidence that the potential benefits of physical activity are especially critical for quality of life issues. Understanding why some adults choose to be active while others do not can provide insight into ways to encourage individuals to be active. Self-determination theory (SDT) is a useful framework for understanding health behaviors and provides a perspective from which to investigate motivation for physical activity. According to SDT, individuals who are self-determined are more likely to engage in a behavior such as physical activity. SDT distinguishes between levels of self-regulation along a continuum ranging from amotivation (a lack of motivation) to intrinsic motivation (engaging for interest and enjoyment). Four levels of regulation conceptualize the steps along the continuum: external, introjected, identified, and integrated. As individuals progress through these levels, behavior becomes more self-determined, from not engaging (amotivation), to engaging because they have to (external); to engaging because they want to (identified). The purpose of this study was to examine how levels of self-determination vary between active and inactive individuals. Participants were 131 (43 males and 88 females) individuals ranging in age from 60 to 79 (M = 69.44) who were recruited from community centers and churches in a southern mid-sized city. They completed the Behavior Regulation Exercise Questionnaire (BREQ; Mullan et al., 1997) to assess levels of self-determination and the Stages of Exercise Change Questionnaire (Reed et al., 1997) to classify their activity levels. A discriminant function analysis revealed that the subscales of the BREQ differentiated between active and inactive participants [canonical r = .50, Wilks' lambda = .752, F (4, 124) = 10.24, p < .001]. The structure coefficients revealed that identified regulation and intrinsic motivation were significant contributors in the discrimination between the groups. The centroid values indicated that active individuals had positive scores on the function, while inactive individuals were negative on the linear combination of the variables. Consistent with theoretical predictions active individuals were more self-determined than inactive participants. Results suggest that practitioners who are trying to encourage older adults to become active should focus on the values and benefits of physical activity with the goal of fostering self-determined motivation.Keyword(s): aging/older adult issues, exercise/fitness/physical activity, health promotion