Although historically bulimia nervosa has been considered to be a disorder influenced primarily by sociocultural forces such as societal emphasis on thinness and attractiveness, over the past decade it has become increasingly clear that biology and genetics contribute substantially to its etiology. Currently, it is believed that combined study of genetic and environmental risk factors may ultimately hold the clue to the question of why when so many young individuals are exposed to societal risk factors, only a small number actually develop frank eating disorders. Genetic research on eating disorders is progressing in the direction of enhanced explication of the phenotype by focusing on behavioral, neurobiological and temperamental variables that may represent core features of the disorder. Such enhanced phenotyping may assist with identifying areas of the genome that may be implicated in susceptibility to these serious and debilitating conditions.