Prognosis in chronic myelomonocytic leukemia (CMML) is unfavorable and the optimal therapy remains uncertain. Currently, allogeneic stem cell transplantation is the only known curative therapeutic option. However, the data available are limited and restricted to small retrospective series. There is even less information on the use of donor lymphocyte infusions (DLI) for this disease. We reviewed our experience of allogeneic stem cell transplantation and DLI for adults with CMML. Seventeen consecutive adults underwent allogeneic stem cell transplantation from related (n=14) or unrelated (n=3) donors. Median age was 50 years (range 26-60). Seven patients (41%) demonstrated relapse or persistent disease at a median of 6 months (range 3-55.5). Five patients underwent DLI for morphologic relapse and one for mixed donor chimerism. Two patients achieved durable complete remissions of 15 months each. The overall transplant-related mortality was 41% (n=7). With a median follow-up of 34.5 months, three patients (18%) currently remain alive and in continuous CR. The current study demonstrates a graft-versus-leukemia effect in CMML, both for allogeneic stem cell transplantation and for DLI. Nevertheless, consistent with reported experience of others, overall outcomes remain less than optimal and unpredictable.