The wide readership of this book by individuals, government officials, scientists and medical specialists is due to concern about the possible hazards of natural and man-made sources of radiation. This publication presents the consequences of exposures to radiation by the use of radiobiological research and results of epidemiological studies. It also summarizes and evaluates sources of human radiation exposures, discusses principal features of radiation risk perception and gives a brief summary and indication of perspectives. Volume 1 comprises the main text of the 2006 report to the General Assembly and 2 scientific annexes: Annex A, epidemiological studies of radiation and cancer, and Annex B, epidemiological evaluation of cardiovascular disease and other non-cancer diseases following radiation exposure.