Although antibiotics are among the most widely used pharmaceuticals, they are also often inappropriately and over-prescribed. Indeed there are increasing predictions that unless we moderate our use of these drugs, bacterial resistance will eventually render them useless. As there are no serious contenders to take the place of antibiotics, including a failure to find new classes of these drugs, it is essential for modern medicine that their efficacy is preserved. Part of the Oxford Infectious Disease Library, this pocketbook is designed to help medical trainees, general prescribers, healthcare workers and students of all biological and medical sciences to understand how antibiotics work, to demonstrate where they might be most appropriate and to make clear the threat of antibiotic resistance. In particular, it will highlight the problems currently seen with bacteria such as MRSA and describe the circumstances leading to their persistence.