Anorexia nervosa (AN) and bulimia nervosa (BN) are related disorders of unknown etiology that most commonly begin during adolescence in women. AN and BN individuals commonly have clusters of puzzling symptoms. Twin studies of AN and BN suggest there is approximately a 50-80% genetic contribution to liability accounted for by additive genetic factors. Psychologically, change may challenge the rigidity of those at risk for AN and BN, and thus open a window of vulnerability. The Price Foundation, a private, European-based foundation, has supported a multicenter international collaboration to investigate the genetics of AN and BN. In an exploration of how behavioral covariates enhanced the linkage signals, Devlin and colleagues evaluated features of ED for the following criteria: consistent relationship to eating pathology; heritability; and relationship to severity of some aspect of the disorder. Some studies evaluating dopaminergic and serotonergic candidate genes for association with AN are reviewed in this chapter.