Asthma remains a major health concern for many Australians. Currently mortality and morbidity rates are very high and have increased substantially over the last 10 years. Within Sydney there is a distinctive pattern of asthma risk with both inner-city and outer western suburbs figuring prominently. This paper looks at asthma within the Sydney metropolitan area. It pays particular attention to the direct and indirect effects of weather and climate on the disease, as well as the interplay between a number of biophysical and socio-economic factors and the role played by outdoor and indoor air pollution. In particular it discusses the relationship between topography, meteorology, air pollution and asthma in Sydney. Finally, it argues that climate change will greatly influence the prevalence and distribution of the disease.