literature were examined, the project did not attempt an exhaustive review of the scientific literature in this field. It should be noted that shortly after the workshop, the National Institutes of Health released a major report on the “Scientific Progress and Future Research Directions” of stem cells, and this document has provided valuable information for the committee’s report (NIH, 2001).

The committee organized the workshop to address key issues in the status of stem cell research by gathering information from scientific leaders in the field. In addition, the workshop provided an opportunity for the committee to hear from both those who support embryonic stem cell research and those who oppose it on ethical grounds. The committee did not attempt to resolve the ethical dilemmas and limits its comments to scientific points intended to clarify or inform the ethical discussion. This report synthesizes the workshop presentations and puts forward the committee’s conclusions drawn from that meeting. In particular, the report addresses the following questions:

• What characteristics of stem cells make them desirable for regenerative medicine?

• Which biological features of stem cells are well established? Which are uncertain?

• What implications do the biological features of different stem cells have for the development of therapeutic applications?

• What opportunities and barriers does stem cell research face, and how are they relevant to medical therapies?

The committee placed off limits the issue of reproductive cloning, which is sometimes linked to stem cell research because in both cases the somatic cell nuclear transfer (SCNT) technique can be used to create embryos (see Box). The interest in this technique for stem cell research is related to the possibility of producing stem cells for regenerative therapy that are genetically matched to the person needing a tissue transplant. The immune system is poised to reject tissue transplants