Various Inhibitors of Apoptosis Proteins (IAPs) are over-expressed in specific types of cancer, and some tumors over-express more than one member of this family of proteins simultaneously. Given that multiple IAPs are simultaneously over-expressed in many cancers, unfortunately antisense or RNA interference (RNAi) methods for assessing function of these proteins are presently often lacking. Therefore, probing the competition of small molecule compounds against either the BIR2 or BIR3 SMAC-binding sites on IAPs, such as XIAP, cIAP1, cIAP2 or other IAPs from human and other organisms will serve as useful tools for elucidating their roles in cancer biology. In this study, we investigated small molecule compounds that selectively mimic the effects of SMAC (second mitochondria-derived activator of caspase) in antagonizing IAPs by causing them to release Caspases. These non-peptidyl chemical inhibitors would have advantages over SMAC peptides, in terms of their greater cell permeability, stability, and in vivo pharmacology. As such, the probe identified in this report ML183 (CID 44176340) met the project’s goal of displaying potent binding affinity and selectivity for the BIR2 domain of XIAP. Moreover, in that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) represents a potent inducer of apoptosis in a wide variety of tumor cells, another valuable finding of this project is that it also promotes cell survival against a challenge by rhTRAIL, an inducer of cell death.