Early B-cell factor (EBF) is a DNA-binding protein required for B-cell lymphopoiesis. The lack of EBF results in an early developmental blockade, including the lack of functional B cells and Igs. Recent studies have elucidated a central role for EBF in the specification of B-lineage cells. EBF directs progenitor cells to undergo B lymphopoiesis and activates transcription of B cell-specific genes in the absence of upstream regulators. How EBF mediates these effects has yet to be thoroughly explored, however, it initiates epigenetic modifications necessary for gene activation and the function of other transcriptional regulators, including Pax5. Together, these observations suggest a molecular basis for the role of EBF in the hierarchical network of factors that control B lymphopoiesis.