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.