African American (AA) women have the lowest physical activity (PA) levels, which contributes to substantial disparities in cardiovascular health and depressive symptoms. There is a need to examine ways to promote PA that are appealing, applicable to clinical practice, and cost-effective. The purpose of this clinical trial is to test the efficacy of the Women's Walking Program (WWP), consisting of a lifestyle PA prescription and "group visit" delivery model, with or without tailored telephone contacts between group visits for increasing adherence to PA and improving health outcomes. Two telephone contact strategies will be compared against a no-telephone control condition: a person-administered contact strategy using brief motivational interviewing and an automated contact strategy using a telephone computer-linked system. Group visits and telephone contacts are designed to increase adherence to lifestyle PA with an emphasis on accumulation of 3,000 steps daily over baseline. The aims of this study are (1) to compare the initial (adoption 24 weeks) and longer-term (maintenance 2nd 24 weeks) effectiveness of the WWP plus person-administered telephone contacts, WWP plus automated telephone contacts, and the WWP without telephone contacts on (a) increasing adherence to lifestyle PA, (b) improving health outcomes (aerobic fitness, body composition, depressive symptoms), (c) improving self-efficacy (confidence in one's ability to be physically active) and outcome expectations (expected benefits to being more active); and (2) to compare cost-effectiveness of the three telephone treatment conditions in relation to adherence to lifestyle PA and health outcomes.