This timely volume brings together essays by an internationally distinguished and diverse group of scholars. Contributors thoughtfully explore the ethical, public policy, and scientific implications of embryonic and adult stem cell research. Part one of the book offers a variety of scientific and public policy perspectives, including essays on stem cell plasticity and using umbilical cord blood as an alternative source of pluripotent stem cells. Part two vigorously examines the ethics of stem cell research and considers issues of social justice, morality, and public policy. Scientific alternatives, a natural law perspective regarding federal funding, and a discussion of the possible moral complicity of Catholic researchers are among the distinctive contributions made to the stem cell research debate by this collection. The objective and balanced discussions contained in this volume serve as an accessible introduction to the bioethical questions, issues, and problems surrounding stem cell research.