Unrelated marrow donor registries.

Although large registries of volunteer, unrelated marrow donors are now operating around the world, potential recipients are frequently unable to identify suitable donors. These searching patients may benefit from 1) improved international coordination and cooperation; 2) a better understanding of the HLA system and the requirements for HLA matching; 3) improved methods for acquisition, storage, and manipulation of HLA-typing data; and 4) the development of alternative hematopoietic stem cell sources.