To investigate whether there are different patterns of development for binge eating and purging behavior among preadolescent and early adolescent girls, we conducted trajectory analyses of those behaviors in 938 girls across 8 waves of data from the spring of 5th grade (the last year of elementary school) through the spring of 9th grade (the first year of high school). Analyses revealed 4 separate developmental trajectories for binge eating behavior (labeled none, increasing, decreasing, and high steady) and 3 separate developmental trajectories for purging behavior (labeled none, dabble, and increasing). Fifth grade scores on risk factors that were both transdiagnostic (negative affect and negative urgency) and eating disorder specific (expectancies for reinforcement from eating and from thinness) differentiated among the trajectory groups, in some cases before the groups differed in the target behaviors. These findings are the first, to our knowledge, to examine developmental trajectories for bulimic symptom onset in youth as young as elementary school. Clinical implications are discussed.