IN spite of the fact that mortality statistics rank malignancy as one of the leading causes of death, the incidence of multiple malignant tumors in the same individual is comparatively rare. Cases in which three morphologically dissimilar tumors occur are regarded as curiosities. The case herewith presented illustrates the occurrence of three such malignant tumors of the uterus. Billroth (1) is credited with the first report on multiple primary malignant growths in the same individual. He emphasized the importance of certain basic criteria before the diagnosis of such a condition could be established. His postulates are as follows: (1) each tumor must have an independent histologic appearance; (2) the tumors must arise in different situations, and (3) each tumor must produce its own metastasis. Mercanton added a fourth prerequisite—that there be no recurrence of the tumors following their removal. The demand for the fulfillment of the third postulate of Billroth, as well as that of Mercanton, is quite as unreasonable in the diagnosis of multiple primary malignancy as in that of a single carcinoma. In the latter case, to diagnose malignancy only in the presence of metastasis would create a deplorable situation. Hurt and Broders (9) and Hanlon (8) felt that the criteria advocated by Goetze are reasonable, and were fulfilled in their cases. They are: (1) the tumors must have the macroscopic and microscopic appearance of the usual tumors of the organs involved; (2) exclusion of metastases must be certain, and (3) diagnosis may be confirmed by the character of the individual metastasis. Burke (2) believed that the reasonable criteria for the diagnosis of multiple primary cancers are: (1) each tumor must be distinct in morphology ; (2) must present a definite histologic picture of malignancy, and (3) must not represent a metastasis. There is considerable difference of opinion as to the incidence of multiple primary malignant tumors in the general cancer population. The work of Warren and Gates (14) is particularly noteworthy in this respect. They collected 1,259 such cases, including 40 of their own. Based on statistics of all the reviewed cases, they found that the frequency of multiple malignancy in cancer patients was 1.84 per cent; on the basis of American statistics it was 3.9 per cent, and in a series of 1,078 autopsies at their clinic the incidence was 3.7 per cent. Counseller and Butsch (4) reviewed the incidence of multiple primary malignant tumors in various series of cases reported and found that the percentage varied from 0.5 to 5.2. Burke (2) reported a series of 46 cases of multiple malignancy, with an incidence of 7.8 per cent—the highest reported in the literature. If we are to place much reliance on the socalled “general cancer-producing factors,” we might consider that an individual affected with one malignant tumor would be fertile soil for the development of other dissimilar tumors.