The regulated oligomerization of proteins is increasingly understood to be an important step in many cellular processes, including signaling, transcription, and protein degradation. The activity of Bax, which is essential for the completion of apoptosis, has been shown to be associated with its oligomerization: homodimerization that appears to facilitate mitochondrial permeabilization during apoptosis and heterodimerization with multidomain anti-apoptotic members of the Bcl-2 family inhibiting this process. Several domains have been identified to be crucial in the homo-/heterodimerization or oligomerization of Bax, especially the so-called Bax homology 3 domain. In this study we show that although the carboxyl terminus of Bax is not implicated in its mitochondrial localization, it has a role in the dimerization process and thus in its activity.