New understandings of radiation and cancer risks are sought through studies of human populations exposed to various forms of radiation. Carcinogenic mechanisms are investigated through molecular studies. Extensive advice is provided national and international agencies. (1) Studies of Chernobyl cleanup workers from Estonia failed to identify an increase in leukemia or thyroid nodular disease; (2) a remarkable increase in thyroid cancer among children from Belarus may be related to fallout from the Chernobyl accident; (3) diagnostic doses of I-131 appeared linked to a small risk of thyroid nodular disease but not cancer; (4) therapeutic doses of I-131 were not linked to leukemia; (5) radiotherapy for breast cancer and Hodgkin's disease increased the risk of lung cancers; (6) total-body-irradiation for NHL increased the risk of leukemia to a greater extent that localized radiotherapy; (7) solid tumors were significantly elevated following bone marrow transplantation among long-term survivors given radiotherapy; (8) occupational exposures to radiation did not increase the risk of breast cancer or leukemia among x-ray technologists; (9) lung cancer was not associated with indoor radon among nonsmoking women in Missouri; the PAR was estimated to be less than 2%; (10) studies of underground miners, however, would predict that 10% of all lung cancers are due to residential radon; (11) ultraviolet light to treat neonatal hyperbilirubinemia was not related to childhood leukemia; (12) parallel analyses of all major thyroid cancer studies indicated little risk for exposures over age 20 and a decreased risk due to fractionation; (13) new studies of atomic bomb survivors increased the occurrence of specific salivary gland tumors and benign adenomatous stomach cancers; (14) hyperparathyroidism was linked to radiotherapy for enlarged tonsils.