Consistent with previous research, BMI was found to be the main predictor of both girls' and boys' dieting over time. Perfectionism predicted boys' preoccupation with muscle mass and dieting. For girls, perfectionism predicted dieting, preoccupation with food, and muscle concerns over the short term but not the long term. Negative feelings predicted both girls' and boys' preoccupation with food over the short term but not the long term. Overall, self-esteem, relationships with parents, and peer relationship were not related to girls' and boys' dieting and preoccupation with food. Unexpectedly, negative feelings, self-esteem, and peer relationships predicted girls' preoccupation with muscle over the long term, but they did not predict the same behaviors and concerns in boys; positive peer relationships predicted high preoccupation with muscle mass for girls. The children were students in 13 primary schools in Melbourne, Australia. Age-appropriate questionnaires were administered to the children to measure the various variables included in the study. The questionnaire was administered to each child twice over a 10-month period. These findings should help health-care professionals identify risk factors for disordered eating and muscle preoccupation at an early age. 5 tables and 48 references