NF-κB proteins were identified in the search for mechanisms that regulate B-lymphocyte-specific transcription of immunoglobulin κ light chain genes. Twenty-five years later, though the function of the κB site in the enhancer remains enigmatic, NF-κB proteins have been shown to have important roles in B-cell development, maintenance, and function. In this review, we summarize the functions of NF-κB in B cells. An overview of B-cell biology that identifies stages in the life of B lymphocytes for the general reader is followed by three sections that examine the role of NF-κB family of proteins in B-cell development, mature B-cell survival and B-cell function. We endeavor throughout to suggest mechanisms and implications of the wide-ranging observations that have been made and conclude by highlighting the need to understand NF-κB-mediated gene expression in more depth.