Members in the Bcl-2 family are critical regulators of apoptosis by either inhibiting or promoting cell death. Bcl-2 homology 3 (BH3) domain is a potent death domain. BH3 domain containing pro-apoptotic proteins, including Bad, Bax, Bid, Bik, and Hrk, form a growing subclass of the Bcl-2 family. Bim is another BH3 domain containing protein which can induce apoptosis. Bim interacts with diverse members in the pro-survival Bcl-2 sub-family including Bcl-2, Bcl-xL and Bcl-w. The messenger RNA of Bim is ubiquitously expressed in multiple tissues and cell lines.