Bacteria and plants produce powerful toxins that can cause a variety of diseases, some of which are lethal for many animal species. The mechanisms of action are common to many of these toxins and represent general pathways for the interaction of a number of biomolecules with target cells, such as binding to specific surface receptors, internalization and translocation across the cell membrane, and interaction with intracellular components. Because of their potency in killing eukaryotic cells, they have been used in the development of novel agents for targeted immunotherapy, and have been termed 'chimeric toxins'.The elucidation of the mechanism of action of protein toxins remains a complex problem, but understanding these mechanisms will open new avenues for the design of novel therapies for the treatment of toxin-related diseases. In Chimeric Toxins: Mechanisms of Action and Therapeutic Applications, the authors review the structure, function and mechanisms of toxic action and investigate their therapeutic applications in medicine, including approaches used to design, express and purify these molecules as well as discussing their characteristics and in vivo efficacy.