The proposed conference is the 14th of the world renowned series, that honors the memory of L. H. Gray. The subject of the conference is very timely because radiation risk estimates are undergoing reexamination by the United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR), National Academy of Sciences, International Commission on Radiological Protection and the National Council on Radiation and Measurements (NCRP). For example, 1) The reassessment of the atomic bomb dosimetry is near completion. The initial risk estimates based on the new dosimetry and the cancer mortality data accumulated up to 1985 suggest that the risk of cancer from exposure to radiation may be greater than previously held. The new dosimetry indicates that the risk estimates for neutrons may not be obtained from data from the survivors at Hiroshima. 2) An ICRU-ICRP joint committee has recommended that the Quality Factor for neutrons should be increased from 10-20. 3) The vexed question of the risk of lung cancer from protracted exposure to the alpha particles, that arise from radon daughters has been examined recently by the NCRP and Measurements and the National Academy of Sciences BEIR IV committee. 4) The exquisite sensitivity of the brain between 8-15 week gestational age has recently led to extensive studies. 5) There is also a considerable body of data obtained recently from molecular chromosomal, cellular and whole animal studies that are important for a sound approach to risk estimates of radiation- induced cancer, genetic and other tissue effects. There can have been few, if any, times that there has been so much new information about radiation effects. It is of great importance that this information is analyzed and interpreted correctly. The aim of the proposed meeting is to review and discuss the epidemiological and experimental data, the methods of analysis, the modeling and methods of extrapolation across species the participants will come from many parts of the world. Much should be learned both within and outside the meeting room. A reasonably high proportion of the speakers will be invited but time will be given over to other presentations and posters, especially by those who have entered the field recently. This grant application is to ensure an appropriate participation of U.S. scientists at the meeting, especially of the younger workers in the field.