Rehabilitation nurses often recommend to aging adults that they exercise. Despite the recommendations and the widespread evidence of its benefits, few older adults exercise. This study examined the predictors of distinct components of exercise behavior: exercise intensity, frequency per week, duration of sessions, and months per year. Social cognitive theory predictors of exercise were measured with previously developed instruments. Interviews were conducted with community-dwelling elders (N = 147). The study constructs accounted for modest to moderate amounts of variance (41% of months per year, 35% of frequency, 35% of exercise intensity, and 20% of episode duration). Self-efficacy was the most important predictor of each construct, with Beta weights ranging from .23 to .53. Barriers significantly predicted months' per year, frequency per week, and exercise intensity, but not the duration of individual exercise sessions. Outcome expectancy predicted only exercise intensity. These findings support the importance of self-efficacy and perceived barriers for most components of exercise behavior.