Mexican Americans are more likely to be obese than non-Hispanic whites, yet little research has been conducted to identify weight control strategies effective with this ethnic group. The purpose of the proposed study is to evaluate an intervention that combines individual- oriented behavioral strategies with more culturally compatible strategies derived from social support theory. A total of 360 obese Mexican-American women between the ages of 18 and 65 years will be recruited from neighborhood units in Starr County, Texas. Subjects will be randomly assigned to either an intervention group or a wait-listed control group. The wait-listed group will receive the intervention one year after the intervention group, and will serve as a no-treatment control group for the pretreatment, post- intervention (6 month), and post-maintenance (12-month) measurement. Both groups will be assessed at six-month intervals for up to two years following the intervention. The intervention will consist of 24 weekly classes with bilingual registered dietitians and behavioral therapists conducting groups of 10 women from neighborhood blocks. The last four weekly classes will instruct women in leading their own self-help groups. During the six-month maintenance period, the peer-led support groups will continue to meet weekly, with additional therapist and dietitian contact provided at one session per month. Continued activity of the peer-led neighborhood groups will be monitored following the maintenance period. Measures of obesity (weight, body mass index, and circumferences) will assess changes in obesity and body fat distribution. Serum glucose, insulin, glycosylated hemoglobin, lipids, and blood pressure will also be measured to determine the effects of weight loss on diabetes and CVD risk factors. Food frequencies will assess changes in dietary intake, and measures of social support, self-efficacy, acculturation, and demographic characteristics will be administered. It is hypothesized that 1) the intervention will result in significant decreases in weight, 2) weight loss will be related to decreases in other CVD risk factors, and 3) social support and adherence to intervention and maintenance strategies will be positively associated with weight loss and maintenance of weight loss.