We report the retrospective outcomes of unrelated donor (URD) transplants in 169 patients with acute lymphoblastic leukemia (ALL) in first complete remission (CR1) who received transplants between 1995 and 2004. Median age was 33 years (range, 16-59 years). A total of 50% had a white blood cell count (WBC) more than 30 ×10 9/L, 18% extramedullary disease, 42% achieved CR more than 8 weeks from diagnosis, 25% had adverse cytogenetics, and 19% had T-cell leukemia. A total of 41% were HLA well-matched, 41% partially matched with their donors, and 18% were HLA-mismatched. At 54-month median follow-up, incidences of acute grade 2-IV, III to IV, and chronic graftversus-host disease were 50%, 25%, and 43%, respectively. Five-year treatmentrelated mortality (TRM), relapse, and overall survival were 42%, 20%, and 39%, respectively. In multivariate analyses, TRM was significantly higher with HLAmismatched donors and T-cell depletion. Relapse risk was higher if the diagnostic WBC was more than 100 ×10 9/L. Factors associated with poorer survival included WBC more than 100 × 10 9/L, more than 8 weeks to CR1, cytomegalovirus seropositivity, HLA mismatching, and T-cell depletion. Nearly 40% of adults with ALL in CR1 survive 5 years after URD transplantation. Relapse risks were modest; TRM is the major cause of treatment failure. Selecting closely HLA-matched URD and reducing TRM should improve results.