Because little is known about risk factors for obesity, the authors tested whether certain psychological and behavioral variables predicted future onset of obesity. The authors used data from a prospective study of 496 adolescent girls who completed a baseline assessment at age 11-15 years and 4 annual follow-ups. Self-reported dietary restraint, radical weight-control behaviors, depressive symptoms, and perceived parental obesity--but not high-fat food consumption, binge eating, or exercise frequency-predicted obesity onset. Results provide support for certain etiologic theories of obesity, including the affect regulation model. The fact that self-reported, weight-control behaviors identified girls at risk for obesity implies that high-risk youths are not engaging in effective weight-control methods and suggests the need to promote more effective strategies.