Occasionally my associates and I have been faced with the problem of making a preoperative or antemortem diagnosis for a child with an obvious endocrine disturbance which presumably has been caused by a new growth in one of the glands of internal secretion. In many instances the correct diagnosis has been obvious, while at other times considerable confusion has arisen among members of the staff regarding which gland was actually the seat of neoplastic disease. It therefore appeared desirable to me to review our material and to set forth herewith typical examples of clinical pictures which are produced by hormonologically active neoplasms of the testicle, ovary, adrenal gland, pineal body and hypothalamic region. The cases here presented do not include all of those which we have been privileged to study, but rather they have been selected so that each case is illustrative of a fairly well defined and easily recognized