Studies of the neuropharmacology of eating behavior demonstrate that monoaminergic neurotransmitters in the brain have an active and important role in the control of food ingestion, in animals and also possibly in humans. The anatomical focus of the animal studies has been the hypothalamus, which appears to play a key role in this process. This structure receives and integrates input from metabolic, hormonal, neurogenic, thermal, and cortical factors, which reflect the nutritional status of the organism, and then it translates this information into signals for inducing appropriate adjustments in food consumption. While this review focuses on the indoleamine, serotonin, with respect to its effects after peripheral and central administration, attention is also given to the catecholamines, which are believed to interact with serotonin in the complex process of controlling eating patterns and appetite for specific macronutrients.