Mass media community-wide physical activity intervention to promote and sustain changes in walking was assessed using a 2-community longitudinal design. The intervention targeted sedentary 50- to 65-year-old residents of Wheeling, West Virginia. Telephone surveys of a probability sample followed cohorts at baseline and at 3-, 6-, and 12-month post-intervention with comparison communities. The intervention, consisting of paid advertisements, public relations, and community participatory planning, attained high levels of awareness and effected significant sustained population-wide changes among the most sedentary in Wheeling.