This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book focuses on the implications of homozygote and heterozygote screening and explains the most recent advances and issues in prenatal diagnosis. It covers the moral, ethical, legal, religious, and psychosocial issues, all of which have known constraints on the utilization of these techniques. The book also covers the educational implications of the scientific advances and the impact that the genetic approach to human disease can have at all levels of health care. It focuses on the recent advances in the prevention of serious, presently untreatable genetic disease, through the use of prenatal diagnosis. The book highlights the benefits that may accrue from the available genetic knowledge if it is applied in human affairs in terms of prevention of disease and the preservation of biological and social equilibrium.