Yury Verlinskyand Anver Kuliev Reproductive Genetics Institute, Illinois Masonic Medical Center, 836 W. Wellington chicago, IL 60657 Although introduction of a first trimester prenatal diagnosis by chorionic viIIus sampling (CVS) has considerably improved the possibility for prevention of genetic diseases, it requires a selective abortion in case of an affected fetus. Following the direction of an earlier prenatal diagnosis and to avoid the need for abortion, preimplantation genetic diagnosis has been initiated based on polar body removal and pre-embryo biopsy. The First International symposium on Preimplantation Genetics, Chicago, September 17-19, 1990, was organized to explore these important developments, to review the state of knowledge in the field, and to address existing problems to be solved for developing and improving current approaches for preimplantation diagnosis of genetic disorders. A growing interest in the subject was obvious from the wide attendance of the meeting: over 250 scientists from 19 countries participated. This was the first attempt to put together the advances in different areas of basic and applied research relevant to Preimplantation Genetic Diagnosis, with the multidisciplinary scientific program including the sessions on embryology, micromanipulation and biopsy, genetic analysis of gametes and pre-embryos, IVF, gene expression and gene therapy, and ethical and legal issues. The deliberations of the Symposium presented in the above mentioned sessions, which comprise the contents of correspond ing sections of the Proceedings, open a newarea in medical research based on the interaction of IVF and New Genetics."