The aim of our study was to evaluate, through the Eurocord and European Group for Blood and Marrow Transplantation (EBMT) registries, outcomes and risk factors for outcomes in adult patients who underwent single or double unrelated cord blood transplantation (UCBT) for myelodysplastic syndrome (MDS) or secondary acute myeloblastic leukemia (sAML). A total of 180 adults with MDS (n=39) or sAML (n=69) were analyzed. Risk factors for outcomes were analyzed using the Fine and Gray method and the Cox model. Median age was 43 (18-72) years. In all, 77 patients (71%) received a single UCBT. Myeloablative conditioning regimen (MAC) was given to 57 (53%) patients. Median numbers of nucleated and CD34(+) cells at freezing were 3.6 × 10(7) and 1.1 × 10(5) kg. At 60 days, cumulative incidence of neutrophil recovery was 78±4% and was independently associated with the number of CD34(+) cells per kg (>1.1 × 10(5); P=0.005) and advanced disease status (blasts <5% at time of UCBT, P=0.016). A 2-year non-relapse mortality (NRM) was significantly higher after MAC (62 vs 34%; P=0.009). A 2-year disease-free-survival (DFS) and overall survival (OS) were 30 and 34%, respectively. In multivariate analysis, patients with high-risk disease (blasts >5% and International Prognostic scoring system (IPSS) intermediate-2 or high in MDS) had significant poorer DFS (hazard ratio (HR): 1.76; P=0.047). In spite of high NRM, these data indicate that UCBT is an acceptable alternative option to treat adults with high-risk MDS or sAML, without a suitable human leukocyte antigen (HLA)-matched donor.