Irradiation of retinoblastoma and other intra- and retro-orbital tumors presents a problem with regard to protection of the lens of the eye. Merriam and Focht (4) and a number of other workers (3, 6, 7) have shown that small doses of ionizing radiation delivered to the equator of the lens will produce an opacity in its posterior portion. With a well collimated x-ray beam, the posterior portion of the globe may be irradiated without difficulty. In using this technic, however, we have seen recurrence of tumor growth anterior to the equator of the eye. The use of high-energy electrons is attractive because they may be readily attenuated in metals. There is also scattering of electrons as they pass into the tissue. Recently Garsou and his co-workers (2) of Liège, Belgium, designed a protective device to shield the lens and allow the treatment of retro-orbital tumors. This device is a complex shield made of brass, lead, and cadmium and was used with high-energy electrons of 20 MeV and an anterior field. The device is attached to the machine and must be precisely aligned with the globe. We have been working with 10 MeV electrons and a protective shield attached to a scleral contact lens to shield the equator of the lens of the eye and allow for adequate treatment of the retina. Use of a copper shield and 10 MeV electrons permits us to stay below the threshold of neutron production in the copper (5). The threshold for neutron production in the two stable copper isotopes together with the half-lives of the resultant activities is given in TABLE I. To test the system, a cylinder of copper was irradiated to 1.2 million rads at 10 MeV and counted in a well-type scintillation counter to detect any isotope production due to a gamma-neutron reaction. No detectable counts above background were found. When the energy of the electrons was raised to 11.8 MeV and the copper was irradiated to 1.2 million rads, the copper yielded 34,424 counts per minute with a background of 152 counts per minute. Use of a 7-mm-thick copper shield made it possible to reduce the dose to the lens to less than 10 per cent of the incident dose. The range of 10 MeV electrons in copper is 6.7 mm (1). Since no electrons can penetrate the copper shield and no neutrons or induced activity is produced, the dose to the lens is due to bremsstrahlung produced by electrons in the copper and electrons scattered from the surrounding field. The isodose curves shown in Figure 1 were obtained with a single anterior field. Behind the shielding there is adequate reduction of dose in the region of the lens, with a 50 to 60 per cent isodose line in the region of the retina posteriorly. With use of a large scleral contact lens with the protective copper attached to the center, the shielding can be aligned properly with the lens of the eye.