[Abstract is probably not needed, since it's a poster] Self-Determination Theory is used to predict individual differences in goal-directed behavior. A fundamental proposition of SDT is that autonomous regulation promotes while controlled regulation hinders behavioral engagement. Unidimensional treatment of regulation is suboptimal. The current study utilizes a multidimensional approach-polynomial regression-to evaluate the interdependent effects of autonomous and controlled regulation on physical activity, comparing it to "person-centered" cluster analyses recently used in an academic domain. Results from two samples of healthy, younger adults demonstrate a positive influence of autonomous regulation but a curvilinear effect of controlled regulation on behavior such that greater activity was associated with moderate levels of controlled regulation-an effect that would not have been identified with previously used methods in SDT research. In older adults with chronic illness, high levels of both regulations predicted greater activity than low levels of both regulations. Results suggest that controlled regulation is not wholly detrimental to behavioral promotion.