In spite of its proved value, radiation therapy with intracavitary applicators is running into mounting opposition because it is difficult to hold radiation exposure of personnel and visitors to permissible levels. By “afterloading,” which we have previously described for uterus applicators (1, 2) and for other intracavitary and interstitial technics (3), radiation exposure during insertion of the applicator can be avoided. In afterloading procedures, an unloaded applicator is inserted first and the radioactive sources are introduced later. Afterloading has been utilized in many recently described uterine applicators (4–7), but the radiation exposure of physicians, nurses, and visitors during the treatment remains a serious problem. In principle, complete elimination of all unnecessary radiation exposure is possible by “remote after -loading,” which has been used for small teleradium bombs for more than twenty-five years (8) and is widely applied in industrial radiography with gamma-ray sources. No satisfactory design for a remote afterloader for intracavitary applicators has been found, however, because many sources of different active lengths are required, a variety of loading patterns may be used, and many sources cannot pass around the sharp bends necessary in several applicators. For these reasons, Walstam's arrangement, for instance, allows remote afterloading of a single tube only (9). A solution to these problems of remote afterloading for intracavitary applicators was found by using small sources of high activity and by cycling them back and forth slowly during the treatment. By changing the length of the cycling movement, and by programming the speed of the source during this movement, sources of any active length and of all loading patterns can be simulated. Three sources of identical activity with cyclic movements from 1 to 15 cm. appear sufficient for remote afterloading of all important intracavitary applicators. Cobalt 60, cesium 137, radium 226, and iridium 192 are suitable as source material. Figure 1 illustrates schematically the arrangement for teletreatment with cycling sources installed at the Memorial Hospital and shows the use of an intracavitary applicator for treatment of a carcinoma of the cervix. The applicator (a) without radio-active sources has been inserted into the uterus and vagina. The patient has been placed on a bed in the treatment room and the applicator has been connected by three plastic tubes (6) to the safe (c). After the door of the treatment room has been closed, the sources (d), which are mounted at the end of long wires (e), are pushed through a mechanism in the control box (f) to their treatment positions in the applicator. For cervix cancer treatment, the two lateral sources remain stationary in the vaginal spacers, while the central source is cycled back and forth over the desired length in the uterine tube.