Morley, Gosnell and Levine discuss the variety of peptides that have been demonstrated to play a role in the modulation of food intake. In particular, the endogenousopioid peptide, dynorphin, represents one of the major neurotransmitters involved in the initiation of feeding. Corticotropin releasing factor is important in the pathogenesis of stress-induced anorexia and may have an etiological role in anorexia nervosa. Calcitonin gene related peptide is also a potent central satiety factor. A number of gastrointestinal peptides including cholecystokinin, bombesin, glucagon, and somatostatin have been shown to provide important input as satiety signals from the gut. The integrative action of many of the neurotransmitters involved in appetite regulation can be conceived as a satiety cascade similar to the classical cascade systems regulating blood clotting and complement fixation. But the authors stress that our increased knowledge of satiety mechanisms has not simplified concepts of pharmacological appetite suppressants.