Enhancers regulate lineage choice and the developmental timing of antigen receptor gene rearrangements. The transcription factor NF-kappaB has been implicated as a key component of the recombination and transcription activation potential of the immunoglobulin kappa chain gene intronic enhancer. Here, I discuss the implications of the new observation that an NF-kappaB binding site-mutated enhancer in the correct biological context does not appear to affect kappa gene expression.