Introduction:St John Ambulance Operations Branch Volunteers have been providing first-aid services at the Royal Adelaide Show for 90 years. The project arose from a need to more accurately predict the workload for first-aid providers at mass gathering events. A formal analysis of workload patterns and the determinants of workload had not been performed.Hypothesis:Casualty presentation workload would be predicted by factors including day of the week, weather, and crowd size.Method:Collated and analyzed casualty reports over a seven-year period representing >7,000 patients who presented for first-aid assistance for that period (63 show days) were reviewed retrospectively.Results:Casualty presentations correlated significantly with crowd size, maximum daily temperature, humidity, and day of the week. Patient presentation rate had heterogeneous determinants. The most frequent presentation was minor medical problems with Wednesdays attracting higher casualty presentations and more major medical categories.Conclusion:Individual event analysis is a useful mechanism to assist in determining resource allocation at mass gathering events providing an evidence base upon which to make decisions about future needs. Subsequent analysis of other events will assist in supporting accurate predictor models.