Stem cells are relatively undifferentiated cells which are the permanent lineage ancestor cells of tissues. Newly developed molecular biological techniques and probes have made possible dramatic advances in our ability to study the lineage development of stem cells. A major impetus to develop these techniques has been to identify specific stem cells for gene therapy purposes. The role that stem cells play in the development of cancer is also an important area. This book provides up-to-date reviews on a wide variety of stem cell systems by world experts. Chapters range from descriptions of the current knowledge of the biology of stem cells, to current molecular biological approaches and clinical implications. Oncologists and cell biologists will find this book of particular interest. It will also be usefule to radiobiologist, biotechnologists, and gene therapists.