4. Patients must have received an allogeneic hematopoietic BMT or PBSCT from a related or unrelated donor that is matched at a minimum at the HLA-A, -B, and -DR loci (i.e., at least a 6 out of 6 match). HLA-A and -B match should be determined by serologic testing, and HLA-DR should be matched by molecular methods.