Bcl-2-family proteins are central regulators of cell life and death. At least three major classes of Bcl-2-family proteins have been delineated, including proapoptotic proteins that contain several conserved regions of sequence similarity (termed 'multidomain'). In mammals, the multidomain proteins (MDPs) of the Bcl-2 family include Bax, Bak, and Bok. The founding member of the MDP group of Bcl-2-family proteins was discovered by Stanley Korsmeyer and co-workers, initiating an exciting area of cell death research. The status of current knowledge about the mechanisms and functions of MDPs is reviewed here, and some areas for future research are outlined. Therapeutic opportunities emerging from a growing understanding of MDPs with respect to their three-dimensional structures, biochemical actions, and roles in disease raise hopes that the foundation of basic research laid by Korsmeyer and others will eventually be translated into clinical benefits, leaving a legacy that benefits the world for many decades.