Polyomavirus enhancer binding protein 2 (PEBP2), also called core binding factor (CBF), is a heterodimer composed of the alpha and the beta subunits. Structural alterations of each of the two subunits generated by recurrent chromosome translocations/inversion are associated with acute myeloid leukemia or acute lymphoblastic leukemia. Chimeric proteins containing a part of either the alpha or the beta subunits have a potential to affect the transcriptional regulation through the PEBP2/CBF site. Structure and function of PEBP2/CBF and possible mechanisms of leukemogenesis caused by the chimeric proteins are summarized.