Drug therapy is the cornerstone of treatment for controlling asthma and preventing and relieving attacks. This report describes the first study to use national data from the Pharmaceutical Benefits Scheme (PBS) to investigate the patterns of asthma medication use in Australia. It examines the effects of sociodemographic characteristics on the frequency of use of these medications, the potency of prescribed medications and the relationships between different classes of asthma medications. The methods used in this study are likely to be applicable to researchers investigating medication use for other conditions and diseases. The results will also be of interest to clinicians and policy makers in asthma.