Background: There is accumulating evidence that individuals with multiple sclerosis (MS) are less physically active than nondiseased populations. One method for increasing the level of participation in physical activity among MS patients involves the identification of factors that correlate with physical activity and that are modifiable by a well-designed intervention. Purpose: This study adopts a social cognitive perspective and examines self-efficacy, enjoyment, social support, and disability as correlates of participation in physical activity among individuals with MS. Methods: We recruited 196 individuals with a diagnosis of MS from the Midwest region of the United States. The participants completed a battery of questionnaires and then wore a belt with an accelerometer for a 7-day period. The data were analyzed using covariance modeling. Results: Enjoyment (γ = .38, p < .001), social support (γ = .15, p < .05), and disability (γ = .18, p < .01) had statistically significant direct relations with self-efficacy, and self-efficacy (β = .29, p < .001) and enjoyment (γ = .28, p < .001) had statistically significant direct relations with physical activity. Conclusions: Future researchers should consider examining self-efficacy and enjoyment as possible components of an intervention that is designed to increase physical activity participation in MS patients. © 2006 by The Society of Behavioral Medicine.