Since most infectious microorganisms inevitably develop resistance to any agents used to combat them, there has been a constant need to produce improved, more potent, antimicrobials. At least in part, the emergence and spread of resistant organisms has been provoked by inappropriate over-use of antibacterials. In the last decade, many fewer new antibacterials have been developed but overall prescribing has continued to increase. Consensus prescribing principles have now been defined with the aim of optimising therapy and preventing further increases in, or even to prompt a reduction in, the prevalence of resistance to antibacterial agents. Whilst it is important to encourage continued development of new classes of antibacterials, it is also vital to make the best use of available agents. The development of new dosages and formulations of amoxicillin/clavulanate allows this agent to continue to fill the important role in therapy which it has occupied, and continues to occupy, 25 years after it was launched.