Since the discovery of mammalian BIK and BAD in 1995, BH3-only proteins have emerged as key activators of apoptotic cell death in animals as diverse as the nematode,Caenorhabditis elegans,and humans. BH3-only proteins have also emerged as integrators of cell-death signals that determine the life-versus-death decision and that transduce this decision to the central apoptotic machinery through their physical interaction with ‘core’ BCL-2 family members, such as BCL-2 or BCL-XL. Currently, eight BH3-only proteins have been identified and characterized in mammals, and there is evidence of functional overlap between them. In contrast, only two BH3-only proteins have so far been identified and characterized inC. elegans,EGL-1 and CED-13, and there seems to be only limited functional overlap between them. Combined with the powerful genetic tools available for the analysis of apoptosis inC. elegans,and the ability to study apoptosis at single-cell resolution in this organism, the absence of extensive functional redundancy makesC. elegansan ideal model for studies on BH3-only proteins. In this study, we will review our current understanding of the role and regulation of EGL-1. We will also briefly summarize studies on CED-13, which was identified more recently.