The nuclear factor (NF)-kappaB family of transcription factors is a key participant in multiple biological processes, most notably in the immune and inflammatory response. Five proteins make up the NF-kappaB family, and these proteins can hetero- and homo-dimerize, giving rise to diversity. Recently, it has been shown that certain members can also interact directly with other transcription factors such as signal transducers of activated transcription, interferon regulatory factor family members and p53, providing further diversity. We propose that this promiscuity might help explain the many of roles of NF-kappaB in specialized cell function and fate. Furthermore, the state of a cell and its cellular background in addition to overall promoter structure and variations in the kappaB target sequence will all define the composition and activity of multimeric NF-kappaB complexes.