Companion Animals Antibiotics are regularly prescribed in practice and it is not uncommon for veterinary surgeons to prescribe them without having irst documented an infection. As such, antibiotics are not always prescribed appropriately. In contrast to many drugs prescribed, the more frequently antibiotics are used, the less efective they become, due to the selection of resistant bacteria. It is, therefore, important that clinicians understand the implications of the overuse of antibiotics and the principles of optimal prescribing. This article aims to review the concerns regarding antibiotic resistance, the role of antibiotics in the development of resistant bacteria, and to provide guidance on how practitioners can reine their prescribing. The problem of emerging multi-resistant bacteria is well recognised in human medicine. The proportion of meticillin-resistant Staphylococcus aureus (MRSA) among all S aureus bacteraemias remained under 3 per cent until 1992, but by 2002 this had risen to 43 per cent (Griffiths and others 2004). In the second volume of her annual report for 2011, the Chief Medical Officer (CMO), Dame Sally Davies, chose to focus on the rise of antibiotic resistance, calling for this 'very real threat' to be placed on the national risk register (Department of Health 2013a). The British Society for Antimicrobial Chemotherapy is currently highlighting the slow development of new antibacterial agents and is actively petitioning the government to increase research in this area (www.antibiotic-action.com).