Smac-N7 Peptide corresponds to the N-terminal seven residues of Smac (second mitochondria-derived activator of caspase) also known as DIABLO. Smac/DIABLO is a mitochondrial proapoptotic protein that activates caspases in the cytochrome c/Apaf-1/caspase-9 pathway by neutralizing inhibitor of apoptosis protein (IAP). Smac-N7 peptide promoted procaspase-3 activation in vitro at around 10 µM and inhibited binding of caspase-9-p12 to the BIR3 (baculoviral IAP repeat 3) domain of XIAP (X-linked IAP). The finding that Smac/DIABLO agonists could enhance the apoptosis-inducing potential of irradiation and chemotherapeutic drugs might lead to promising new candidates for cancer treatment.