This book about protein-protein Interactions as drug targets, targeting the MDM2-p53 protein-protein interaction for new cancer therapeutics, the development of small-molecule IAP antagonists for the treatment of cancer, protein-protein interaction targets to inhibit HIV-1 infection, inhibitors of protein-protein interactions paramyxovirus fusion ? a focus on respiratory syncytial virus, rational design strategies for developing synthetic inhibitors of helical protein interfaces, and the discovery of navitoclax, a Bcl-2 family inhibitor.