A comparison of the radiation distribution with several methods of radium application for the treatment of carcinoma of the endometrium was made from the results of an earlier experiment (8). It was concluded from that study that the multiple-capsule packing method described by Heyman (5) was superior from the standpoint of the resultant radiation fields. The experimental conditions described, however, necessarily excluded many variables encountered in practice which must be taken into consideration in order to achieve a basis for more accurate comparison. In discussion of the study, Dr. E. H. Quimby and Dr. James Heyman both suggested that more practical aspects of the multiplecapsule method be further explored. Its adaptability to uteri varying in size and shape was the specific problem brought out, and to that question the present study is devoted. Many years ago Sampson emphasized the variations in the size and shape of uteri containing endometrial carcinoma (10). The configuration of the endometrial cavity may become distorted by the growth of the carcinoma itself or as a result of concomitant benign conditions. Among the latter, myomata are frequent offenders. The incidence of myomata in conjunction with carcinoma of the endometrium has been stated by several authors to be about 30 per cent, although there is little evidence to indicate an actual etiological relationship between the two conditions (11). The usual figure given for the incidence of myomata in women over thirty years of age, in autopsy material, is 20 per cent (9). Sampson further pointed out the technical difficulties which variations ill the size and shape of the uterus may cause in the effective intrauterine application of radium. Distortion of the cavity may cause the sources to be displaced away from small tumors, or large tumors themselves may deflect the intracavity sources from the bases and actively growing portions of the neoplasm. There is danger of rupture of the uterus in the presence of such distortion and irregularity. Also, endometrial carcinoma is a post-menopausal disease and may occur in atrophic uteri. Achieving a uniform field of radiation under such conditions, where only a few sources can be used, is not an easy matter. Furthermore, introduction of radium sources into these small cavities with fibrotic walls and a stenosed canal is a difficult and potentially dangerous procedure. Since it is difficult, even after examination under anesthesia and dilatation and curettage, to outline the exact size and configuration of some of these tumors, the variations become important. Theoretically, the multiple-capsule method of radium implantation, which utilizes as many small sources as are needed to fill the available space, best adapts itself to the variations in the geography of the endometrial cavity. Whether this adaptability acts toward uniformity of radiation distribution is a question of practical importance.