Transcriptional regulation during myelopoiesis. The coordinated production of all blood cells from a common stem cell is a highly regulated process involving successive stages of commitment and differentiation. From analyses of mice deficient in transcription factor genes and from the characterizations of chromosome breakpoints in human leukemias, it has become evident that transcription factors are important regulators of hematopoiesis. During myelopoiesis, which includes the development of granulocytic and monocytic lineages, transcription factors from several families are active, including AML1/CBF beta, C/EBP, Ets, c-Myb, HOX, and MZF-1. Few of these factors are expressed exclusively in myeloid cells; instead it appears that they cooperatively regulate transcription of myeloid-specific genes. Here we discuss recent advances in transcriptional regulation during myelopoiesis.