Apoptosis, or programmed cell death, occurs during normal cellular differentiation and development of multicellular organisms. Apoptosis is induced by certain cytokines including TNF and Fas ligand of the TNF family through their death domain containing receptors, TNFR1 and Fas. Cell death signals are transduced by death domain (DD) containing adapter molecules and members of the ICE/CED3 protease family. A novel DD containing molecule was recently cloned from mouse, human and monkey and designated Daxx. Daxx is a death domain containing important intermediate in the Fas mediated apoptosis. Daxx binds specifically to the Fas death domain and enhances Fas induced apoptosis and activates the Jun N terminal kinase (JNK) pathway. It is widely expressed in fetal and adult human and mouse tissue, indicating its important function in Fas signaling pathways.