All of animal cells may be intrinsically programmed to self-destruct. The activation of apoptosis causes cell death instantaneously unless the cell death is inhibited by survival signals. The various antiapoptotic molecules as well as proapoptotic factors have been identified. The apoptotic cell death requires the interplay of a multitude of factors. These related factors are organized in a tight and efficient manner in the mediation and regulation of apoptotic signaling. The members of IAP family and iNOS can inhibit caspases along extrinsic or intrinsic pathways. Bcl-2 family mainly regulates the intrinsic pathway in cytoplasm. Mitochondrial proteins Smac/Diablo and Prss25/HtrA2/Omi modulate IAP activity as well. Transcription factors such as NF-κB and p53 mediate apoptosis through up- or downregulation of apoptosis-related gene expression in nuclei. The detailed regulatory mechanisms still need to be determined.