This contract is for a series of collaborative epidemiological studies of cancer risk among Japanese A-bomb survivors, using resources of the Radiation Effects Research Foundation (RERF) in Hiroshima and Nagasaki, Japan. Objectives include: identification of specific studies; identification of collaborating scientists; preparation of research protocols and study designs; collection of data; data analysis; and report preparation. For the period of this report, studies of interest included surveys of breast, lung, thyroid, and colorectal cancer, and laboratory studies of culturedskin fibroblasts from cancer cases and controls.