Early in 1955 a kilocurie cesium-137 teletherapy machine was installed in the Medical Division of the Oak Ridge Institute of Nuclear Studies. After much preliminary physical work involving radiation protection surveys and isodose plotting, the machine was made available for limited clinical trial. The present report deals with the early clinical impressions obtained in treating 11 patients. Structural and physical particulars of this teletherapy device have been published elsewhere (1). Only a few remarks will be made here on some points bearing directly on its clinical application. the machine The machine consists essentially of a shielded 1,500-curie cesium-137 source that is capable of movement in four directions— tilt, vertical, horizontal, and circular (Fig.1). By means of a rather complex mechanical and electronic set-up, these movements can be co-ordinated to achieve a wide variety of rotational patterns. Up to the present time, clinical use has been made only of arcs of rotation and of conical rot...