There is growing evidence that adult stem cells age. This process can result in alterations in the number and function of stem cells, leading to distinct phenotypic outcomes in different organ systems. This publication provides an outstanding overview of this emerging field. The molecular causes of stem cell aging remain to be defined. Stem cell aging can involve cell-intrinsic as well as cell-extrinsic alterations affecting the stem cell niche or the macroenvironment. Stem cells have a longer life span than other cell populations and retain a capacity to proliferate and differentiate in adult organs. The aging of adult stem cells plays a key role in the decline of organ maintenance and regenerative potential during aging and during the end stage of chronic diseases. In addition, it can contribute to stem cell transformation and carcinogenesis. Molecular Mechanisms of Adult Stem Cell Aging will appeal to scientists working in the fields such as stem cells, aging, regeneration and cancer. This subject matter should be of interest to physicians and scientists specializing in geriatric medicine, internal medicine, and surgery. It is also likely to be an invaluable resource for medical students and biologists who wish to enhance their understanding of molecular and stem cell biology.