This study prospectively tracked the self-change attempts of 200 New Year's resolvers over a 2-year period in order to more fully understand the coping determinants of maintenance and the natural history of lapses and relapses. Seventy-seven percent maintained their pledges for 1 week but only 19% for 2 years. Successful resolvers reported employing significantly more stimulus control, reinforcement, and willpower than the unsuccessful over the 2 years; social support and interpersonal strategies failed to predict success before 6 months but did so thereafter. Counterconditioning and fading were retrospectively nominated as the most efficacious coping strategies; paucity of willpower and failure of stimulus control were reported as the most hindering to maintenance. Fifty-three percent of the successful group experienced at least one slip, and the mean number of slips over the 2-year interval was 14. Slips were typically precipitated by a lack of personal control, excessive stress, and negative emotion.