Valid case definitions are necessary to understand etiology and assess effectiveness of treatment and prevention strategies. However, achieving such validity is complicated for diseases and disorders that lack a definitive biological test or rely on symptom manifestations, such as eating and other psychiatric disorders1. To address this, investigators propose classification systems of variable utility with an understanding that there is no clear “gold standard” approach. For example, although case definitions based on DSM diagnoses may imperfectly model disordered eating, they can be invaluable to researchers and practitioners who hope to predict and understand the course of illness or response to treatment1,2. However, it may be developmentally inappropriate to extrapolate classification approaches based on adult studies to understanding presentations in youth. For example, among adults there is one body mass index cut-off for obesity, but among children one must take into account age and gender to interpret whether a child’s body mass index is sufficiently elevated to be considered obese3. With eating disorders, it is possible that eating and weight concerns present differently and/or at subthreshold levels more frequently in preadolescence, adolescence, and young adulthood; if so, applying a classification system without acknowledgment of these differences could misrepresent the prevalence and public health impact, and may miss opportunities to identify causes, consequences, or correlates of the disorders. This could be particularly disconcerting in adolescence, which is when eating disorders often onset and perhaps an ideal time to intervene4,5. One technique for empirical classification is latent class (LC) analysis, which clusters subjects based upon their observed response patterns into mutually-exclusive classes6. A compelling feature of the LC modeling approach is that, relative to other categorical and dimensional empirical classification approaches, LC analyses make relatively fewer and weaker assumptions. Specifically, LC analyses require that, while observed covariates may be highly correlated unconditionally, the observed covariates are uncorrelated within a class7. Although a strong assumption, clinical homogeneity within classes is an attractive feature. In contrast, dimensional approaches to classification, although often parsimonious and in certain circumstances more biologically plausible, require many additional assumptions about the distributions of and relationships between the observed covariates and unobserved dimensions. For example, dimensional approaches, such as exploratory factor analysis, require the assumption that the errors for factors are independent, have a mean of zero, have equal variance across factors, are multivariate normally distributed, and for orthogonal models, the factors are independent. LC analysis has been a popular tool in addressing eating disorder classifications (see review by Crow et al 20117), but has been primarily employed in clinical samples of adult patients. As only a small minority of individuals who report disordered eating symptomatology in nationally- representative studies seek treatment for their eating/weight problems 4, it may often be preferable to draw inferences from community-based rather than treatment-seeking samples. Few LC studies have analyzed younger populations and most only included treatment-seeking cases. LC analysis has only been used in one community-based sample of youth, but the 12–23 year old females were analyzed together8. In order to identify possibly prodromal, subclinical, or additional presentations that may arise during the age periods of high incidence4,5, it is essential to evaluate possible classifications in more finely-grained age strata. Several questions remain unanswered. Is it possible to develop an empirically based classification structure for female preadolscents, adolescents, and young adults? If so, would the classification structure vary across developmental stages, or could a similar set of classes be found throughout youth and young adulthood? Would these classes resemble those seen in empirically-based classification structures for adults? Would these classes be clinically relevant, i.e., would they be predictive of course or adverse outcomes? Answering these questions is essential for future research to understand the natural history of eating disorders and for improvements in early detection, prevention, and treatment. With all these questions in mind, the primary goal of the current study is to empirically derive an eating disorder classification structure for females across developmental stages using LC models, potentially allowing classification to vary through youth and young adulthood. To evaluate the predictive validity of this classification structure, we assessed the association between class membership and the co- occurrence and incidence of drug use, binge drinking, and high depressive symptoms.