Self-efficacy is posited in social cognitive theory as fundamental to behavior change. Few health behavior studies have examined self-efficacy prospectively, viewed it as part of a reciprocal behavioral process, or compared self-efficacy beliefs in the same population across different behaviors. This article first discusses self-efficacy in its theoretical context and reviews the available prospective studies. Second, it explores self-efficacy as a predictor of disease management behaviors in 570 older women with heart disease. Although the R2 statistics in each case were modest, the construct is shown to be a statistically significant (p<.05) predictor at both 4 and 12 months postbaseline of several disease management behaviors: using medicine as prescribed, getting adequate exercise, managing stress, and following a recommended diet. Building self-efficacy is likely a reasonable starting point for interventions aiming to enhance heart disease management behaviors of mature female patients.