The aim of this study is to detect any genetic differences between bone marrow and PBSC unrelated donors, post donation and confirm or refute the observations of "long-term genetic or epigenetic effects" published by Nagler et al[Nagler,A. et al. Exp.Haem (2004) 32;122-30]. The employment of more sensitive methods such as iFISH and gene array analysis to assess any permanent genetic changes, our primary objective, will make our study more robust.