AIM: A major heatwave occurred in Australia in early 2009 with considerable and varied health impacts in South Australia (SA) and Victoria. The aim of this study was to investigate the heat-adaptive behaviours of older people in these states. METHODS: A computer-assisted telephone survey of 1000 residents of SA and Victoria aged 65 years or older was conducted at the end of summer 2010-2011. RESULTS: The majority of respondents reported undertaking heat-adaptive behaviours. In SA, there was a significantly higher proportion of households with air conditioning compared to Victoria, and a higher recall of heat-health messages. In both states, self-reported morbidity during heatwaves was higher in women, persons with poorer health and those with cardiovascular conditions. CONCLUSION: An increase in global temperatures in conjunction with an ageing population is a concern for public health. Our findings suggest acclimatisation to hot weather may influence behaviours and health outcomes in older people.