[Truncated abstract] This thesis describes the epidemiology and outcome of acute asthma managed by ambulance paramedics, in the metropolitan area of Perth, Western Australia, for the period of 1990 to 2001. The primary aim of this thesis was to determine demographic, socio-economic and clinical trends for ambulance transported patients with asthma, their outcomes and how they have changed over time. The Perth metropolitan area, located in the south-western corner of Western Australia (WA), accounts for 72% of the state’s population, which was approximately 1.3 million people at Census 2001. This thesis was structured around the analysis of twelve years of St John Ambulance (WA) data. Ambulance data was linked using probabilistic matching techniques to the Western Australian Data Linkage System, custodian of links to thirty five years of morbidity and mortality data of the state’s population . . . Unique geography, a monopolistic ambulance service and access to extensive linked data provided ideal conditions for this population-based epidemiological study of patients with asthma who were transported by ambulance. Observed trends in age and gender characteristics of patients, ambulance codes and temporal variables appear to be consistent over time. Monitoring trends in the use of ventilation procedures recorded in hospital data provided useful indicators for describing the epidemiology of severe, lifethreatening asthma in the prehospital setting. Findings from this study were found to be consistent with published literature.