This study examined the effects of 2 aerobic exercise regimens on exercise participation, fitness, eating patterns, treatment adherence, and weight change in 49 obese women undergoing a year-long behavioral weight loss program. Participants were assigned randomly to weight loss treatment plus either group- or home-based exercise. All participants were instructed to complete a moderate-intensity walking program (30 min/day, 5 days/week). Group exercise participants were provided with 3 supervised group exercise sessions per week for the first 26 weeks and with 2 sessions per week thereafter. Home exercise participants were instructed to complete all exercise in their home environment. After 6 months, both conditions displayed significant improvements in exercise participation, fitness, eating patterns, and weight loss. At 12 months, the home-based program showed superior performance to the group condition in exercise participation and treatment adherence; at 15 months, participants in the home program demonstrated significantly greater weight losses than those in the group program.