The purpose of this protocol is to collect blood, bone marrow, urine, stool, buccal mucosa and/or both malignant and non-malignant tissue from patients who are either being evaluated for enrollment, are consented to NIH Clinical Center treatment protocols, or are receiving therapy for their disease through home health care providers. Since a substantial proportion of the clinical and translational research in the Hematology Branch involves patients undergoing allogeneic stem cell transplantation, this protocol will also be open to people identified as suitable HLA-compatible donors for patients undergoing evaluation for or already enrolled in an allogeneic stem cell transplant protocol or receiving a stem cell transplant through their home health care providers. These HLA-compatible donors will serve as a source of peripheral blood mononuclear cells (peripheral blood draws or leukapheresis) for use in evaluating allogeneic graft versus host and graft-versus-tumor effects.