The history of X rays in biological research began almost simultaneously with Roentgen's discovery of his new rays. The history may be unique because of the remarkable collaboration of physicists, chemists, biologists and clinicians-collaborations which have produced and are continuing to produce major contributions to both biological and medical science. These contributions include the use of X rays to investigate molecular structure and function, the first demonstration of induced mutagenesis, the delineation of the cell cycle, the initiation of in vitro and in vivo cloning of mammalian cells, and original studies in DNA repair. The following is a personal overview of the history of some of these developments and their relationship to areas of current biological research. In each case an attempt has been made to trace developments from an early observation or observations to the current day. The history has been divided into two segments, each of approximately 50 years. This division seems appropriate because the separation occurs at approximately the same time as developments which were to play a major role in determining the future of radiation research. (C) 1995 by Radiation Research Society
