Within recent years the idea has become firmly established in the minds of physicians that a variety of morbid phenomena are due to autointoxication - are, in other words, attributable to certain poisonous metabolic products. This view, it is true, is not new, for it was familiar to the physicians of past generations and was a part of the teachings of the medical folk-lore of long ago. It was not, however, until Bouchard and his pupils published their investigations on the subject of autointoxication that this theory attained the dignity of a scientific doctrine. At first we German physicians were by no means inclined to accept the theory of autointoxication that was being so enthusiastically proclaimed. Of late years, however, our attitude has become more friendly to the doctrine; this change of front is due to the fact that a number of toxic products of metabolism have actually been isolated and their mode of origin in the organism and their pathologic effect determined to the satisfaction of the former critics of the doctrine. We do not, of course, know all that we should properly know about the poisonous metabolic products that we incriminate in so many morbid states; but in a large group of important symp tom-complexes we are fortunately in possession of a number of facts that suffice to ground the doctrine of autointoxication on a solid chemical basis.