Exercise is the best predictor of long-term weight loss. This study evaluated two strategies for improving exercise adherence and long-term weight loss in obese outpatients. Obese men and women (N = 193) were randomized to 1 of 5 treatment groups for 18 months: standard behavior therapy (SBT); SBT with supervised walks (SW) 3 times per week; SBT + SW with personal trainers (PT), who walked with participants, made phone reminders, and did make-up SW; SBT + SW with monetary incentives (I) for completing SW; and SBT + SW + PT + I. Both PT and I enhanced attendance at SWs, the combination producing the best adherence. Increased walk attendance did not result in higher overall energy expenditure, however, and long-term weight loss was also not improved. Post hoc analyses suggest that the level of exercise needed for successful long-term weight loss is much higher than that usually recommended in behavioral treatment programs.