G-CSF and GM-CSF have been shown in each clinical setting to reduce the duration of neutropenia, with the exception of the scant data available in the unrelated bone marrow transplant setting. These growth factors also have been shown to have no leukemogenic effect during the observation periods of the trials discussed. In MDS, one major randomized trial has demonstrated a reduction in incidence of infection. This has not yet been demonstrated in AML and allogeneic BMT. Data from ongoing and future trials will be helpful in elucidating their effect on treatment-related morbidity and overall survival.