This proposal is for modest support for a book on the epidemiology of human chromosome disorders. The goal is to pull together and synthesize from a number of diverse sources both published and unpublished all the available data on the frequency, known and suspect etiologic factors, transmission, suspect associations, prevention, and impact of these numerous conditions, as well as evolution of historical understanding of their epidemiology. The volume will be of use, it is hoped, in i) ensuring more, accurate and consistent genetic counseling with regard to risks of chromosome disorders, thus contributing to improvement of health care delivery in this area, ii) help workers in the field by providing ready access to summaries and syntheses of work (much of which at present is scattered in diverse journal articles, conference reports, doctoral theses, and symposium proceedings) thus acting as a "guide" to the literature, iii) enable workers to gain an appreciation of the historical evolution of knowledge in the field, iv) stimulate individuals to begin to work upon outstanding problems in the field of which they were not previously aware, v) help workers in the field put their own work in the context of previous work by others, vi) ultimately through the above goals to diminish the burden of these abnormalities in our species. The book will consider all human "constitutional" chromosome disorders, i.e., those present in the zygote or arising early in embryogenesis. These have major impact upon morbidity and mortality in our species, causing, it has been estimated about 30% of all embryonic and fetal deaths, about 5% to 7% of infant and early deaths in childhood and about 20% of recognized mental retardation.