Bone marrow, peripheral blood and cord blood are all sources of hematopoietic stem cells for allogeneic transplants. These sources differ in regard to collection methods, cellular content and transplant outcomes. In the related setting, use of peripheral blood stem cells, when compared to bone marrow, results in faster engraftment and may confer a survival benefit in advanced disease but also may lead to an increase in chronic graft-versus-host-disease. While cord blood stem cells are the simplest to collect and allow the greatest flexibility in HLA matching, they contain the lowest stem cell dose leading to the slowest engraftment. In this review, we discuss the advantages and disadvantages of these different stem cell sources as well as areas for further research.