Antimicrobial stewardship (AMS) aims to optimise antimicrobial prescribing to maximise effectiveness and minimise potential adverse effects such as toxicity and the emergence of resistant organisms. Effective AMS programs have been shown to reduce inappropriate antimicrobial use, reduce institutional bacterial resistance rates, improve patient outcomes and reduce healthcare costs. AMS is mandatory for Australian public and private hospital accreditation under The National Safety and Quality Health Service Standard 3.14. The clinical microbiology service (CMS) is an integral part of effective AMS programs. Key CMS activities include: • the provision of best practice diagnostic tests for a range of pathogens to deliver accurate and timely results, enabling clinicians to de-escalate or cease unnecessary antimicrobials • cascade reporting of antimicrobial susceptibility reports • providing comments in microbiology reports to help guide appropriate antimicrobial therapy • clinical liaison for critical results and high risk patient groups such as intensive care • education to prescribers about appropriate antimicrobial use • the development and review of appropriate clinical guidelines • the production of an annual cumulative antibiogram to guide empiric antimicrobial therapy and inform local clinical guidelines • the provision of surveillance data on resistant organisms for infection control purposes.