Until 1987, the Radiation Effects Research Foundation (RERF) and its predecessor organization, the Atomic Bomb Casualty Commission (ABCC), utilized a dosimetry system developed in the sixties, the so-called Tentative Dosimetry System 1965 or T65D1,2), which later, after some revisions, became known as T65DR3). In the late seventies increasing doubt was raised (particularly in the Oak Ridge, Lawrence Livermore, and Los Alamos National Laboratories and at Science Applications International Corporation) on the correctness of the assumptions and the use of models underlying T65D, culminating in two symposia in 1981, one during the annual meeting of the Radiation Research Society in Minneapolis, Minnesota4), and the other one under the aegis of the U.S. Department of Energy in Germantown, Maryland5). Shortly thereafter, a major effort was initiated to evaluate the entire system of dosimetry then extant, and to design a new system if indicated. This undertaking, involving tens of investigators and millions of dollars and yen, resulted in the publication of a thousand-page, two-volume description of a new dosimetry system, christened Dosimetry System 19866). Following publication of these volumes, RERF received data bases and computer programs that form the core of the DS86 computational system currently in use at RERF.