Prudent antibiotic prescribing is a cornerstone of efforts to control the emergence and spread of antimicrobial resistance and to reduce the occurrence of Clostridium difficile associated diarrhoea, and is also currently the subject of a joint Working Party of the British Society for Antimicrobial Chemotherapy and the Hospital Infection Society. An article in this issue of the Journal describes a cluster randomized trial of an intervention to improve antibiotic prescribing using TREAT, a computerized decision support system. The results from this trial provide a significant contribution to the development of evidence-based prescribing of antibiotics.