Examined the role of social support provision and efficacy cognitions in adherence to a prescribed exercise regimen. Data from 86 adults indicate that when used as time-varying covariates, the social provisions of reassurance of worth, attachment, and guidance were significantly associated with intraindividual fluctuations in program adherence. Specifically, Ss with a greater sense of self-worth were more likely to adhere throughout the program, whereas the effects of Ss’ perceptions of greater attachment, although generally related to sustained adherence, fluctuated over time. Findings also suggest that Ss perceiving higher levels of guidance were less likely to adhere during the early and concluding stages of the exercise program. Although synchronous covariation existed between efficacy cognitions and attendance, self-efficacy was not predictive of intraindividual change in attendance over time.