Body dissatisfaction, a measure of body image, physical attractiveness, and body mass index were assessed in the same 115 participants at ages 13, 15, and 18 years. Sex differences in body dissatisfaction emerged between 13 and 15 years of age and were maintained at 18. Over adolescence, girls increased, while boys decreased, their body dissatisfaction. Body dissatisfaction was weakly related to others' ratings of the adolescents' physical attractiveness and their body mass index. The results support the idea that, overall, adolescents' body image has little to do with how others perceive them, but once developed remains constant through much of adolescence.