Although there are many books on the bacterial resistance issue, this one focuses on the main problem posed by resistant organisms: multi-resistance. Resistance and multi-resistance arise as consequences of a complex set of biological, social and economic forces, briefly depicted in chapter 1. Bacteria gain multi-resistance in a number of ways, covered thoroughly in chapters 2 to 5: gathering individual resistance genes in single genetic elements, activating responses to environmental stress, and growing in biofilms. Two of the most dangerous pathogenic organisms (methicillin-resistant S. aureus and vancomycin-resistant enterococci) pose a threat because they are always multi-resistant; these organisms are reviewed in chapter 6. Finally, chapter 7 is devoted to explain a different way to look into the evolution of resistance -a way that can be used in the search for new antimicrobial drugs. With 563 references, the book contains detailed, up-to date information, as well as general models explaining the evolution of multi-resistance.