The discovery of TRAIL (TNF Related Apoptosis Inducing Ligand), also referred to as Apo-2, is in an era of intense research because TRAIL induces many cancer cells to undergo programmed cell death (apoptosis), while having no effect on normal cells. This important protein deserves extensive review at a formative time in the devlopement of our knowledge concerning its mechanism of action and the ways in which it can be used as a cancer chemotherapeutic agent. Consequently, this voume reviews the current status of research on TRAIL.