 Allogeneic and autologous bone marrow transplantation is currently the only curative option for many patients with life-threatening hematologic illnesses and malignancies. Peripheral blood stem cell PBSC infusion has been associated with systemic toxicities including arrhythmias, hypertension, and organ dysfunction. It has been thought that the preservative dimethyl sulfoxide DMSO that is frequently used to store frozen PBSCs may be the etiology of the adverse effects that occur during the infusion. However, we hypothesize that the red blood cells that rupture upon thawing infused with the graft release free hemoglobin which scavenges nitric oxide. This can lead to systemic vasoconstriction and organ dysfunction. In this protocol, we will monitor subjects who are undergoing PBSC transplantation with either fresh grafts that lack DMSO or frozen whole grafts. We will also evaluate patients who receive purified stem cell grafts, which will contain negligible red blood cells and associated free hemoglobin. We will then measure the frequency of infusion-related systemic toxicity and organ dysfunction between the groups. 