Nuclear factor-κB (NF-κB)/Rel transcription factors have been suspected since their discovery to play a pivotal role in chronic and acute inflammatory diseases. It now seems that aberrant regulation of NF-κB could also underlie autoimmune diseases and different types of cancer. Recently, NF-κB and the signalling pathways that regulate its activity have become a focal point for intense drug discovery and development efforts. Given the large number of major ailments in which aberrant regulation of NF-κB has been observed or is suspected, such efforts seem well justified. This review will discuss recent progress in the development of drugs that inhibit NF-κB activation, and consider their potential applications in inflammatory and autoimmune diseases, as well as cancer.