POSEIDON is a project funded by the European Commission (EC), its name actually refers to an acronym which stands for : Promoting Optimisation, Safety, Experience sharing and quality Implementation for Donation Organisation and Networking in Unrelated Haematopoietic Stem Cell Transplantation in Europe. It is a 3-year long project that has officially started the first of June 2007 involving 8 partners from several European countries (the partners) in the intent to improve the safety of Hematopoietic Stem Cells Transplantation and a more egalitarian access to this therapy throughout European Union. This will be done through networking, multidisciplinary experience sharing and education. In order to achieve these goals we will use results from a previous EU project : MADO (The mother project), as well as some other previous works from international or European Non Governmental Organisations (such as the World Marrow Donor Association) and their networks.