When treating uterine cancer with intracavitary sources of radium or its equivalent, identification of the uterine cervix and correlation with these sources is an important part of the procedure. Sherman (1) studied the radiation distribution around radium sources in 23 instances of locally residual recurrent disease in 422 patients. In 18 in which roentgenograms were available, he found that failure could definitely be attributed to inadequate distribution of the radioactive sources on and around the tumor. The main causes of failure were a gap between the intrauterine radium and the vaginal radium and slippage of the radium out of the uterus. No roentgenograms were available for the retrospective study in the remaining 5 cases. Placing a silver “seed” at the cervix is the most reliable way to identify the cervix and to detect displacements. Clips are often difficult to attach at the apex of the contracted vault; they may also tear off due to the friability of the tissues. Opaque thread in the vaginal pa...