The authors advise that the motivation to change from unhealthy diet and exercise practices among adolescents similar to this sample will stem from the promotion of positive attitudes about the self and one's ability to achieve positive change, as well as an increase in the sense of one's value as an individual within one's peer and ethnic group. Fifty-five percent of the boys and 31 percent of the girls were overweight as measured by weight in relation to height (body mass index) and age. A high body mass index (BMI) was related to weight-control efforts, including dieting and exercise. Heavier adolescents were more likely to report being unhappy with their weight and the wish to weigh less. Overweight youth also reported being less healthy physically. For girls, heavier weight was significantly linked to quantity of cigarette smoking. A negative body image related to being overweight was associated with lower self-esteem, anxiety/depression, and feelings of not being accepted in the peer group. Satisfying peer relationships and feelings of social acceptance in early adolescence influenced the development of more positive feelings about body image in later adolescence for both boys and girls. For boys, but not for girls, positive ethnic-identity experiences contributed to the development of a positive body image. Separate questionnaires were used to survey the youth and their parents at two time points 2 years apart, at ages 13 and 15. Self-reports measured BMI, body image, and health and weight control behaviors. Instruments measured psychological adjustment, self-esteem, peer acceptance, and sense of ethnic identity. 5 tables, 2 figures, and 55 references