The BMT program at Princess Margaret Hospital performed 105 transplants using cryopreserved peripheral blood stem cells (PBSC) from related allogeneic donors. The outcomes were compared with those of a historic control of 106 patients transplanted with freshly procured PBSC. The infusions were tolerated with limited toxicity related to nausea/vomiting or bradycardia, correlated with the total amount of DMSO infused. The average viability of the total nucleated cell (TNC) population after thawing was 71%. The survival of clonogenic progenitors amounted to 75% for colony-forming unit-granulocyte-macrophage (CFU-GM), 69% for burst-forming units erythroid (BFU-E), and 78% for colony-forming units granulocyte-erythrocyte-monocyte-megakaryocyte (CFU-GEMM). In contrast, colony-forming units megakaryocyte (CFU-MEG) was significantly more cryosensitive with recovery rates of 39%. The number of viable CD34(+) cells transplanted was correlated with the number of transplanted viable CFU-GM (P < .001), BFU-E (P < .001), CFU-MEG (P < .001), and CFU-GEMM (P = .049), but not with the TNC dose. The number of transplanted CD34(+) cells was correlated with engraftment of neutrophils (P = .012) and platelets (P = .013). The outcomes of cryopreseved or fresh PBSC transplants (PBSCT) with respect to engraftment of neutrophils (P = .178) and platelets (P = .785), lymphocyte recovery (P = .926), acute (P = .113), and chronic graft-versus-host disease (P = .673), recurrence (P = .295), nonrelapse mortality (P = .340), and overall survival (P = .668) were not significantly different. It is therefore reasonable to consider the option of cryopreserved allografts.