To compare the effectiveness of stage-matched vs. social-cognitive physical activity interventions in a work setting. Both interventions were designed as minimal-contact, self-help programs suitable for large-scale application. Randomized trial. Participants were randomized into one of the two intervention groups at baseline; the follow-up assessment was conducted 1 month later. A large, public university in the southeastern region of the United States. Employees from two academic colleges within the participating institution were eligible to participate: 366 employees completed the baseline assessment; 208 of these completed both assessments (baseline and follow-up) and met the compliance criteria. Printed, self-help exercise booklets (12 to 16 pages in length) either (1) matched to the individual's stage of motivational readiness for exercise adoption at baseline or (2) derived from social-cognitive theory but not matched by stage. Standard questionnaires were administered to assess stage of motivational readiness for physical activity; physical activity participation; and exercise-related processes of change, decisional balance, self-efficacy, outcome expectancy, and goal satisfaction. The two interventions were equally effective in moving participants to higher levels of motivational readiness for regular physical activity. Among participants not already in maintenance at baseline, 34.9% in the stage-matched condition progressed, while 33.9% in the social-cognitive group did so (chi2 = not significant). Analyses of variance showed that the two treatment groups did not differ in terms of physical activity participation, cognitive and behavioral process use, decisional balance, or the other psychological constructs. For both treatment groups, cognitive process use remained high across all stages, while behavioral process use increased at the higher stages. The pros component of decisional balance did not vary across stage, whereas cons decreased significantly between preparation and action. Minimal-contact, one-shot physical activity interventions delivered at work can help people increase their participation in regular physical activity. Stage matching may not necessarily add value to interventions that otherwise make good use of behavior change theory. The findings also reinforce the importance of barrier reduction in long-term adherence. A limiting factor in this study is that employees in the earliest stage of change (precontemplation) were not well-represented in the sample.