Bcl-2 protein family members, including anti-apoptotic and pro-apoptotic members, act on mitochondria controlling the fate of cell between life and death. In healthy cells, Bcl-2 protein family displays specifically cellular location that fit to their functioning: anti-apoptotic members are localized predominantly to the cellular inner membranes, especially the outer mitochondrial membrane, and most of the pro-apoptotic members exist mainly in the cytosol. Following death stimuli, Bcl-2 protein family members can be regulated through mechanisms such as phosphorylation, proteolysis and protein-protein interaction etc, by which one of the main consequences is the shift of the cellular location of proapoptotic members. Translocation of proapoptotic members from cytosol to mitochondria will result in mitochondrial dysfunction and the release of apopogenic factors in the mitochondrial intermembrane space, culminating in apoptosis.