Infectious diseases caused by bacteria remain a leading cause of death worldwide. Many of the antibiotics developed to combat bacterial infections have been rendered almost impotent due to the rapid evolution and spread of antibiotic resistance. A common and major resistance mechanism, the efflux system, enables bacteria to extrude structurally divers antimicrobials, facilitating survival in toxic environments. This book reviews the most important current research and summarizes the most spectacular discoveries in the field.