Apoptosis plays a major role in normal organism development, tissue homeostasis, and removal of damaged cells. Disruption of this process has been implicated in a variety of diseases such as cancer. The Bcl-2 family of proteins is comprised of critical regulators of apoptosis that can be divided into two classes: those that inhibit apoptosis and those that promote cell death. Bak, a pro-apoptotic Bcl-2 family member, is an oligomeric protein that localizes to the mitochondria. It is thought to share significant functional homology with Bax, another pro-apoptotic Bcl-2 family member, as disruption of bak or bax has little effect on cell death, but mice lacking both genes display multiple developmental defects and cells lacking bak and bax show decreased apoptotic capability.