Bcl-2 is now recognized as a potent inhibitor of apoptotic cell death. It has been reported that Bcl-2 is located in the mitochondria, endoplasmic reticulum, and nuclear membrane in some cell lines, and it is not expressed in normal human and rat liver. An earlier study showed that Bcl-2 is an inner mitochondrial membrane protein. On the contrary, the following investigations using immunoelectron microscopy demonstrated that Bcl-2 resides predominantly in the mitochondrial outer membrane. In this study, using a cryo-sectioning immunogold labeling technique and immunoblotting, we carefully determined the subcellular localization of Bcl-2. Here we report that Bcl-2 is expressed in normal rat liver, and it is located predominantly in the inner membrane and crista rather than in the outer membrane of mitochondria.