Book excerpt: 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.Selected Contents:* Crystal Structure of RANK Ligand involved in bone metabolism* Promoter of TRAIL-R2 Gene* Monoclonal Antibodies against TRAIL* Modulation of TRAIL signaling complex* TRAIL in the airways* FLIP Protein and TRAIL-Induced Apoptosis* TRAIL and Ceramide* TRAIL and Viral Infection* TRAIL and Malignant Glioma