Anorexia nervosa (AN) is a severe and potentially lethal disease of the young woman. It is defined as an anxious disorder not to gain weight, and an obsessive behavior regarding body weight and physical appearance. Different and variable patterns of behaviour are observed. This article focuses on the renal problems observed in anorexic patients. Anorexia is often associated with severe electrolyte disturbances, such as hypokalemia and hypophosphatemia, and alterations of water metabolism with hyponatremia and edema. Hypokalemia and chronic dehydration may contribute to the development of renal failure. Even end stage renal disease can be observed in these patients. A better understanding of the pathophysiology might improve treatment of patients suffering from AN.