OBJECTIVE AND BACKGROUND: Reattendance rates at hospitals and emergency departments (ED) can provide a valuable marker of the quality and effectiveness of clinical care. Linked hospital and ED data from New South Wales and Victoria, Australia, were used to examine reattendances for asthma. METHODS: Hospital and ED data were linked to identify individuals who reattended hospital or ED for asthma within 28 days of an initial attendance. The sociodemographic characteristics that predicted reattendance were examined using logistic regression. RESULTS: There were 139,043 attendances for asthma between July 2000 and June 2003 attributed to 95,042 people. Overall, 7.1% of people reattended for asthma within 28 days. There was a significantly higher risk of reattendance among females (odds ratio (OR) 1.09, 95% confidence interval (CI) 1.03-1.14), people who lived in areas of greater socioeconomic disadvantage (OR 1.20, 95% CI 1.12-1.29) and Indigenous people (OR 1.15, 95% CI 1.00-1.32). Reattendance rates differed among age groups (P < 0.001), with the lowest rate being in 5- to 14-year-olds. CONCLUSION: The availability of linked hospital and ED data has provided a rare opportunity to investigate predictors of reattendance for asthma. Surveillance of trends in reattendances for asthma can be used to monitor the effectiveness of interventions to improve asthma control across the continuum of care, particularly in higher-risk groups such as Indigenous people, young children and those with greater socioeconomic disadvantage.