An exhaustively researched account of the ""opening act of Nazi genocide"": the murder of approximately 70,000 physically and mentally handicapped German citizens. Friedlander (History/Brooklyn College; coeditor of the 26-volume Archives of the Holocaust series) notes how Nazi political leaders, bureaucrats, physicians, and scientists believed in and brutally practiced eugenic beliefs and extended them to the conviction that there is ""life unworthy of life."" He spells out how the so-called ""euthanasia"" program first initiated in 1939 evolved from forced sterilization of the disabled to the establishment of killing centers disguised as hospitals. As news of the program leaked out and protests mounted, Hitler ordered a halt to the program, code-named T4, in August 1941; by then, it also encompassed Jews, Gypsies, Poles, and others. However, T4 continued and served as a model for the Holocaust, in which many T4 personnel participated. Friedlander's book is particularly valuable in noting the methodology of T4 and its strong parallels with that of the ""Final Solution"": the use of secrecy and deception, including sinister euphemisms (those murdered were referred to as ""decontaminated""), meticulous record-keeping by a vast bureaucracy, the technology of gas chambers, and the plunder of the victims and their families. The whole grisly story generally is told well, although Friedlander nearly buries the reader under a mountain of detail, particularly in writing about the bureaucracy of murder and in providing countless mini-profiles of the killers. However, the latter do demonstrate how the doctors active in T4 tended to be younger than their uninvolved colleagues and were motivated by ""a mixture of ideology, careerism and greed."" This somewhat daunting work at times makes for very tough reading but as the one of first English book-length studies of the ""euthanasia"" program to date, it unquestionably is a most valuable contribution to the history of Nazism and of the Holocaust.