Title: The Role of Quantum Mechanics in Structure-Based Drug Design Author: Kenneth M. Merz Jr Department of Chemistry The Pennsylvania State University Abstract: Semiempirical quantum chemical (QM) methods have had tremendous impact on our understanding of chemical and biological systems. In this presentation we will focus on the application of semiempirical QM methods to solve relevant problems in structure-based drug design (SBDD). For example, we will describe recent application of these methods to the scoring of protein-ligand poses, NMR spectroscopy, X-ray spectroscopy, pairwise energy decomposition of protein-ligand complexes and in QM/QSAR applications. Finally, we will summarize our vision of the future application of quantum chemistry to SBDD.