The extent to which dysregulation of serotonin function in the central nervous system may contribute to core symptoms in patients with bulimia nervosa and anorexia nervosa is currently an area of intensive psychobiological investigation. Preclinical and clinical studies have demonstrated the involvement of the neurotransmitter serotonin in the regulation of food intake, suggesting that impaired serotonin-mediated satiety signals could contribute to patterns of recurrent binge eating. Other symptom patterns in patients with eating disorders, including mood dysregulation, impulsivity, and obsessionality, as well as therapeutic response to serotonergic agents, suggest involvement of serotonergic pathways. With a primary focus on serotonin function, this article reviews clinical studies of neuroendocrine and behavioral response to pharmacological challenges, levels of neurotransmitter metabolite in cerebrospinal fluid, and platelet studies. Controlled clinical trials involving pharmacological treatment with serotonergic medications are summarized. Considerations for future research are discussed.