An international workshop on Radiation Cataractogenesis, organized by Dr. Kazuo Neriishi, was held March 9–10, 2009 at the Radiation Effects Research Foundation (RERF) in Hiroshima, Japan and included 34 epidemiologists, ophthalmologists and radiobiologists who reviewed current evidence concerning radiation cataract type, incidence and potential threshold dose in irradiated human cohorts. Laboratory and animal studies that help elucidate underlying pathological mechanisms of cataractogenesis were also reviewed. Current recommendations and guidelines for lens ionizing radiation exposure were discussed in light of the new data. A summary of the presentations, as well as the general discussion and conclusions, is reported here. In view of recent evidence suggesting that current NCRP and ICRP assumptions of radiation dose–effect thresholds for radiation cataracts may be set too high, Dr. Toshiteru Okubo, Chairman of RERF, charged the workshop participants to freely discuss the published data as well as new reports as they bear on the international dose limits for eye protection. Thirteen presentations were made that reviewed or updated recent data from epidemiological and biological research groups, along with an extended discussion period seeking to characterize the current status of knowledge and further research needs.