The receptor interacting protein RIP is a death domain-containing serine/threonine kinase which associates with FAS or the TNF-R1 binding protein TRADD. RAIDD (RIP-associated ICH-1/Ced-3 homologous protein with a death domain) has been identified as a RIP binding protein that also associates with members of the caspase family, providing a link between activation of the TNF-Rs and the triggering of the cysteine protease cascade. The amino-terminal domain of RAIDD shares significant homology with the prodomain of ICH-1 and mediates the binding of RAIDD to this cysteine protease.