 The obesity epidemic observed in recent years can be largely attributed to an obesogenic environment that encourages overeating and sedentary lifestyles. Behavioral weight control treatment, the most empirically validated intervention approach, produces initial weight losses of 10; however, maintenance of initial weight loss and behavior change has not been achieved. These disappointing long-term results may reflect the fact that participants are given only minimal, indirect instruction on how to change their environment to support their new weight-regulating behaviors. While in theory, the behavioral model emphasizes environmental antecedents and consequences of eating and exercise, in practice, only 1 to 2 sessions in standard treatment are dedicated to stimulus control-types of skills. By teaching weight control skills in a contextual vacuum, participants remain vulnerable to the same environmental influences that maintained their unhealthy eating and exercise habits. Given that the majority of eating and exercise is home-based, a logical step in strengthening behavioral treatment and moving toward an ecological model of behavior is to expand the focus of treatment from the individual to the individual plus their home environment. We propose to test the long-term impact of a behavioral weight control program designed to directly modify both the physical and social home environment of weight loss participants. Two hundred overweight and obese men and women will be randomly assigned to either 18 months of standard behavioral treatment SBT or 18 months of standard behavioral treatment plus direct modifications to the home environment SBTHome. SBTHome will incorporate many strategies that have shown promise in improving weight loss e.g., food and exercise equipment provision, spouse involvement but will be the first to study both physical and social factors within the home simultaneously and will be the longest examination of the home environment conducted to date. Participants and spouses will be assessed at baseline, 6, 12, and 18 months. We hypothesize that by broadening the focus of treatment from the individual to the individual plus their home environment, SBTHome will produce both better long-term weight loss and better maintenance of initial weight loss and behavior change. This home environmental approach, if successful, has potential applications to the maintenance of other important health behaviors. 