Prophylaxis for surgical site infection (SSI) is often at variance with guidelines, despite the prevalence of SSI and its associated cost, morbidity, and mortality. The CareTrack Australia study, undertaken by a number of the authors, demonstrated that appropriate care (in line with evidence- or consensus-based guidelines) was provided at 38% of eligible SSI healthcare encounters. Here, we report the indicator-level CareTrack Australia findings for SSI prophylaxis. Indicators were extracted from Australian and international clinical guidelines and ratified by clinical experts. A sample designed to be representative of the Australian population was recruited (n=1154). Participants' medical records were reviewed and analysed for compliance with the five SSI indicators. The main outcome measure was the percentage of eligible healthcare encounters with documented compliance with indicators for appropriate SSI prophylaxis. Of the 35,145 CareTrack Australia encounters, 702 (2%) were eligible for scoring against the SSI indicators. Where antibiotics were recommended, compliance was 49% for contaminated surgery, 57% for clean-contaminated surgery and 85% for surgery involving a prosthesis: these fell to 8%, 10% and 14%, respectively (an average of 11%), when currently recommended timing of antibiotic administration was included. Where antibiotics were not indicated, 72% of patients still received them. SSI prophylaxis in our sample was poor; over two-thirds of patients were given antibiotics, whether indicated or not, mainly at the wrong time. There is a need for national agreement on clinical standards, indicators and tools to guide, document and monitor SSI prophylaxis, with both local and national measures to increase and monitor their uptake.