The hematopoietic stem cell (HSC) field has rapidly grown in the past several years as new technologies have been developed and the older tried and true methods have been used in new ways. Major advances in the isolation of HSC and progenitor subsets have been sparked by the gene expression array technologies, leading to the identification of new markers for prospective isolation. The first edition of Hematopoietic Stem Cell Protocols is a very thorough resource covering historically the basic techniques that have been published extensively over many years. To put together, a follow-up to this excellent book has been a hard act to follow. The intent of this book is to be distinct and not duplicate but to build on the strong basic assays and include updated approaches for the combination of phenotypic and functional analyses. This second edition of Hematopoietic Stem Cell Protocols thus aims to provide timely protocols developed in the HSC field since the last comprehensive review in this series. The approaches described in this book should be readily useful for the basic science researcher, especially those familiar with the use of mouse genetic models. The chapters in this book are geared toward the laboratory-based researcher and the development of pre-clinical studies to apply HSCs toward treating blood diseases more effectively.