The purpose of this study is to evaluate the effect of a preintervention physical activity preparatory course on physical activity, and social, cognitive, and transtheoretical constructs. The sample included 82 low-income, multiethnic women (75% Latina) who completed an 8-week course designed to prepare them to become more active prior to randomization into a 10-month physical activity intervention. Participants completed precourse and postcourse measures. Paired-comparison t tests showed increases in knowledge, perceived social support for exercise, minutes of walking per week, and total cognitive and behavioral processes following the preparatory course. Perceived barriers and self-efficacy for exercise did not change from precourse to postcourse. Preintervention preparatory courses may be an effective way to increase social and cognitive constructs associated with physical activity behavior, potentially yielding a greater effect from subsequent interventions. (Contains 2 tables and 2 figures.)