Purpose. In this study, we examined the influence of self-efficacy in predicting stage of change (SOC) movement, without intervention, over a 1-month period for smoking cessation, exercise adoption, and dietary fat reduction. Design. The design of this study was longitudinal. Patients' stage of change and self-efficacy were assessed at baseline, and stage of change was reassessed at a 1-month follow-up. Patients were categorized as (1) Regressors (moved backward at least one stage), (2) Stables (no change), or (3) Progressors (moved forward at least one stage). Chi-square analyses were used to determine the ability of self-efficacy to predict stage movement at 1-month follow-up. Setting. The data were collected at a large, inner city, academic hospital in the southeastern United States. Patients were attending primary care clinics. Subjects. Five hundred fifty-four low income, predominantly African-American, individuals attending primary care clinics were participants in the study. Measures. Previously validated scales of stage of change and self-efficacy from Prochaska's laboratory were used in this study. Results. Results showed statistically significant differences between predicted and actual SOC movement for smoking cessation, exercise adoption, and dietary fat intake reduction. Baseline self-efficacy ratings were significantly related to stage progression, regression, and stability of stage of change for all three health behaviors. Thirty-seven percent of smokers who were predicted to progress on the basis of their self-efficacy scores progressed. For exercise adoption and dietary fat reduction, 50% and 44%, respectively, of individuals expected to progress at least one stage on the basis of self-efficacy scores progressed. Conclusion. Self-efficacy influences SOC movement for smoking cessation, dietary fat reduction, and exercise adoption.