As part of a long-standing collaboration with the Radiation Effects Research Foundation (RERF) in Hiroshima and Nagasaki, NCI is continuing epidemiological and multidisciplinary studies of cancer risk in relation to radiation dose among a cohort of 94,000 atomic bomb survivors. This project has been critically important in understanding the late effects of radiation exposure, now 60 years after the events occurred. Among the most significant developments is the publication of the second report on the incidence of solid cancers in the Life Span Cohort of atomic bomb survivors adding 11 years of follow-up, using new dose estimates, and the updated incident solid cancer risks among people exposed to atomic-bomb radiation in utero and during early childhood. Major findings include: a linear radiation dose response with no threshold for solid cancer, with indication of lifelong persistence of radiation risks; highly age-dependent radiation-related risk of leukemia that has decreased gradually over the years but remains significantly elevated; and decreasing radiation related solid cancer risk among those exposed in-utero as they begin to age. Investigations led by NCI have provided novel insights into modification of radiation related cancer risk by other carcinogenic factors, e.g., endogenous estrogens for breast cancer, UV exposure for non-melanoma skin cancer, hepatitis B and C viral infections for hepatocellular carcinoma, and smoking for lung cancer.