Purpose: A non-radiation-containing regimen of busulfan and cyclophosphamide (BU/CY) was evaluated for toxicity, relapse, and long-term survival in patients who received allogeneic bone marrow transplantation (BMT) for myelodysplasia (MDS). Patients and Methods: Thirty-eight patients with MDS, including eight with therapy-related MDS, were prepared for BMT using BU/CY. Results: Fourteen patients remain in first remission 18 to 60 months posttransplant. Five patients relapsed after BMT, and four of these patients died. Eight additional patients died of acute or chronic graft- versus-host disease (GVHD), and 11 died of regimen-related toxicity, primarily systemic mycoses. Overall survival rate at 2 years was 45% (95% confidence interval [CI], 0.30 to 0.61), with a 24% probability of relapse (95% CI, 0.10 to 0.49). Regimen-related toxicity was manifested primarily as hepatic dysfunction in 72% of patients, with 16% developing overt venoocclusive disease (VOD). Conclusion: Non-radiation-containing preparative regimens offer long-term survival in allogeneic BMT for MDS that is comparable to that of radiation-containing regimens, and are useful in patients with therapy-related MDS. Monitoring BU levels may reduce regimen- related mortality and improve survival.