Although the diverse functions served by the nuclear factor-I?B (NF-I?B) pathway in virtually all cell types are typically employed to deal with stress responses, NF-I?B transcription factors also play key roles in the development of hemopoietic cells. This review focuses on how NF-I?B transcription factors control various aspects of thymic T-cell and myeloid cell differentiation that include its roles in hemopoietic precursors, conventional I?I? T cells, CD4 + regulatory T cells, natural killer T cells, I?I T cells, macrophages, and dendritic cells. A? 2012 John Wiley Sons A/S.