Evi-1 is a transcription factor with two sets of zinc finger domains. The temporally and spatially restricted pattern of Evi-1 expression in embryonic tissues suggests a role of Evi-1 in organogenesis and morphogenesis in mouse development. Mice lacking Evi-1, which die within the first few weeks of life with multiple defects in embryonic development, suggest that Evi-1 is essential for developmental cell proliferation, vascularization, and cell-specific signaling at midgestation. In hematopoietic cells, Evi-1 expression is restricted at a transient stage of myeloid cell differentiation. Constitutive expression of Evi-1 in hematopoietic cells, which is caused by retroviral insertions or chromosomal translocations and inversions, is closely associated with myelogenous leukemias and myelodysplastic syndromes in mice and humans. In the aspect of potential therapeutic approaches, some pharmaceutical drugs or antisense oligonucleotides that repress Evi-1 expression would be useful for the treatment of Evi-1-induced neoplastic tumors.