Diseases of various kinds, from mild functional disorders of important organs to serious anatomic lesions may determine the attitude the physician should take toward the question of reduction cures in obesity. Simple and clear as the matter lies in uncomplicated obesity the question becomes difficult and complicated in obesity combined with other diseases. Generally speaking we more often are confronted with the necessity of combating obesity for the sake of influencing the course of complicating diseases than of treating obesity for its own sake. It is quite impossible to discuss all the points of view that have to be considered in this place for in order to do this it would be necessary to discuss nearly the whole field of pathology. I must limit my dissertation therefore to a discussion of the most important features of the question at issue and can only treat of the most important disturbances that should induce us to institute reduction treatment; in this way we will learn to recognize those disorders that call for reducing treatment even though the degree of obesity per se does not apparently warrant this therapy.