In this multicenter retrospective study, the outcomes of 234 patients with myelodysplastic syndrome (MDS) who underwent transplantation between 1995 and 1999 from HLA-identical siblings were analyzed according to the hematopoietic stem cell source used, that is, bone marrow (BM, n = 132) or granulocyte colony-stimulating factor-mobilized peripheral blood progenitor cells (PBPCs, n = 102). There were 69 cases of refractory anemia (RA), 86 RA with excess blasts (RAEB), 75 RAEB in transformation (RAEB-t), and 4 unclassified MDS at diagnosis. The International Prognostic Scoring System was intermediate-2 or high in 104 of the 158 available scores. Multivariate analyses focused on transplantation-related mortality (TRM), 2-year treatment failure incidence, and survival. Use of PBPCs reduced the median duration of neutropenia and thrombocytopenia by 4 and 12 days, respectively. The incidence of acute GVHD was similar whatever the graft type used. Chronic GVHD was more likely to have occurred with PBPCs (odds ratio [OR], 1.62; 95% confidence interval [CI], 0.87-3.02). Two-year TRM was significantly reduced with PBPCs (relative risk [RR], 0.33; 95% CI, 0.15-0.73; P <.007), except for patients who had either RA or high-risk cytogenetics. The 2-year treatment failure incidence was significantly decreased with PBPCs, from 38% to 13% (RR, 0.22; 95% CI, 0.10-0.48; P <.001). Estimate of the 2-year event-free survival was 50% with PBPCs versus 39% with BM. In multivariate analysis, the outcome was significantly improved with PBPCs (RR, 0.27; 95% CI, 0.13-0.52; P <.001), except for patients with either RA or high-risk cytogenetics. In conclusion, PBPCs might be preferred for allogeneic transplantation in MDS patients at high risk for relapse on the basis of morphologic criteria because the use of this hematopoietic stem cell was associated with lower treatment failure incidence and improved survival.