Bulimia nervosa (BN) and Anorexia Nervosa (AN) are currently classified as eating disorders (ED). Both disorders are the product of complex interaction between physiological and psychological and social processes; they are characterized by abnormal eating behavior. However, patients with BN differ from AN in their nutritional state and response of treatment with serotonin-selective reuptake inhibitor (SSRI) as well as frequency of comorbidity of mood and anxiety disorders. Although biological mechanisms of both BN and AN are largely unknown, excess of both feeding-stimulatory and feeding inhibitory signaling in AN have been indicated. This report reviews data that point to the hypothesis that dysregulation of monoaminergic and new peptidergic circuitry controlling food intake and energy expenditure play a major role in the eating behavior of BN.