Irradiation of rabbit eyes with high-energy electrons was used to test the inhibition of experimental intraocular proliferation and retinal detachment, produced by intravitreal implantation of 250,000 homologous fibroblasts. After irradiation with 2,000 rad, started 5 days after implantation, 45% of eyes (9 of 20) still manifested traction detachment. When the dose was increased to 3,000 rad and radiation treatment was started 1 day after implantation, proliferation and traction detachment were observed in only 10% of eyes (2 of 20). No acute damage to retinal tissue or nerve fibers was observed. Because it is easily available, simple in application and dose adjustment, and without toxic side effects, radiation therapy should be considered as an effective alternative to drug treatment for the inhibition of intraocular proliferation and detachment. Statistically significant results of this investigation suggest its use combined with surgery in certain reproliferative cases in man.