The proteolytic activity of the cysteinyl aspartate-specific proteases, named caspases, mainly connotes their central role in apoptosis and inflammation. In this review we report on recent data on the role of caspases in the activation of nuclear factor kappaB (NF-kappaB), a transcription factor that fulfils a central role in innate and adaptive immunity, in cellular stress responses and in the induction of anti-apoptotic factors. Two different mechanisms by which caspases activate the NF-kappaB pathway are discussed.