Purpose. To examine behavioral factors related to successful weight maintenance. Methods. Subjects were 90 middle-aged participants who attended a weight loss program and were followed for one year. The subjects were classified into either successful weight maintainers (maintained a weight loss of 5% or more from their initial weight for one year) (SWM) or unsuccessful weight maintainers (USWM), and weight control practice, stress, obstacles, support, and self-efficacy during the program and follow-up period were compared. Results. SWM had mean loss of 12% from their initial weight during the program. They showed a greater improvement in their regularity of eating, walked more, and felt less stress regarding their increased physical activity than the USWM. During the follow-up period, significantly more SWM participants had self-efficacy (for measuring weight, practicing dietary objective, and assessing the practice and keeping records), actually kept records and measured weight more than the USWM participants. In contrast, more USWM participants felt stress about measuring weight. Conclusion. In addition to a substantial initial weight loss due to an increased amount of physical activity, having a higher self-efficacy and consistently keeping records of one's activities, as well as regularly weighing themselves, may be important for successful weight maintenance.