This book is a multidisciplinary study investigating the field of embryonic stem cells from different professional perspectives. The book has both a biological/medical perspective, dealing with new technological possibilities in medical research and putative clinical therapy, as well as an ethical perspective, including philosophical and theological approaches focusing on the question of the moral status of human embryos. The researchers involved in the study represent different scientific, philosophical and theological positions, and different views concerning the ethical problems at issue. The idea is that cooperation in such a group creates a critical and self-critical dialogue where differing opinions and evaluations can be reexamined. There are several reasons for writing this book:(a) The stem cell field is a very ‘hot’and promising field of research in many countries around the world.(b) At the same time it is a controversial field, especially with regard to some of the ethical implications. Ethical aspects of stem cell research are highly debated among people from biology, medicine, law, philosophy, theology etc.(c) There are different regulations concerning stem cell research within the legislation of various countries.(d) The public discussions among citizens and among politicians are to a large extent dividing the populations of many countries in the West and the East.(e) On this background I decided to bring together professionals from different disciplines involved in the topic in order to start an international and interdisciplinary work concerning some of the burning ethical questions raised by stem cell research and eventual therapy. This work was carried out as a two year research project financially supported by the Norwegian Research Council, with the title “The moral status of human embryos with special regard to stem cell research and therapy”. The reason for this approach was that the international debate has been especially concentrated on the use of embryonic stem cells.(f) Selected presentations from this project have later been rewritten with a view to publishing these final texts in a common book. On the one hand the contributions give comprehensive and updated information on the current situation within stem cell research, and on the other hand they give a presentation and an evaluation of the ethical argumentation related to the field.(g) Finally, I am of the strong opinion that the debate going on in many countries concerning stem cell research, and especially the use of human, embryonic stem cells, will profit substantially from a sufficient overview of the different aspects relevant for an ethical evaluation. vii