Successful Bone Marrow Transplantations with unrelated donors can be performed providing that donor and recipient are totally HLA-A, B, DR identical. To find such a suitable donor it is necessary to type a large pool of volunteers for HLA in histocompatibility laboratories. We have built a network of 36 micro-computers AT 286 for updating local files and for translating data to the national file of donors maintained on a main computer (VAX 8250). The main computer communicates regularly using modems with local computers in order to update data and exchange information. After one year of functioning, users are well satisfied with the computers system which locates regularly potential donors for recipients waiting for a graft.