Volume 4 of "Advances in Medicinal Chemistry" is comprised of six chapters on a wide range of topics in medicinal chemistry, including molecular modeling, structure-based drug design, organic synthesis, peptide conformational analysis, biological assessment, structure-activity correlation, and lead optimization. Chapter 1 presents an account about amino acid-based peptide mimetics corresponding to b-turn, loop, helical motifs in proteins as a probe of ligand-receptor and ligand-enzyme molecular interactions. Chapter 2 addresses new facets of the medicinal chemistry of the important anticancer drug Taxol(r) (paclitaxel). Chapter 3 relates an account of the search for new drugs for the treatment of malaria based on the natural product artemisinin. Chapter 4 applies computational chemistry to the evaluation of compound libraries for biological testing. Chapter 5 describes the construction of a 3-dimensional molecular model of the human thrombin receptor, the first protease-activated G-protein coupled receptor (PAR-1), as a means to explore the intermolecular contacts involved in agonist peptide recognition. Finally, Chapter 6 describes the research conducted at Merck on inhibitors of farnesyl transferase as a potential treatment for human cancers.