Objective: To examine sexual orientation group differences in eating disorder symptoms in adolescent girls and boys. Method: Cross-sectional associations were examined using multivariate regression techniques using data gathered in 1999 from 10,583 adolescents in the Growing Up Today Study, a cohort of children of women participating in the Nurses' Health Study II. Results: Ninety-two percent of the cohort described themselves as heterosexual, 5% as mostly heterosexual, 1% as lesbian/gay/bisexual, and 2% as unsure. Both mostly heterosexual girls and boys had greater concerns with weight and appearance and were less happy with their bodies compared with same-gender heterosexuals (all p < .05). Compared with heterosexual girls, the mostly heterosexual girls were more likely to vomit/use laxatives to control weight (odds ratio 1.7; 95% confidence interval = 1.2-2.6) and to binge eat (odds ratio 2.3; 95% confidence interval = 1.4-3.8) in the past year. Compared with heterosexual boys, gay/bisexual boys were more concerned with trying to look like men in the media (p < .05) and more likely to binge (odds ratio 15.2; 95% confidence interval = 3.3-69). Compared with heterosexual girls, lesbian/bisexual girls were happier with their bodies (p < .05) and less concerned with trying to look like women in the media (p < .05). Conclusions: Mostly heterosexual girls and boys are a newly identified group at increased risk of eating disorder symptoms. Gay/bisexual boys were also at increased risk. J. Am. Acad. Child Adolesc. Psychiatry, 2004;43(9):1115-1123. Key Words: eating disorders, weight concerns, sexual orientation, gay, lesbian, bisexual, homosexual, Growing Up Today Study.