WHAT WE NEED TO KNOW: What is an agreed definition of chronic obstructive pulmonary disease (COPD) for epidemiological research? What are the predicted values of gas transfer (TLCO) for Australian populations? What is the prevalence of asthma and COPD in people over the age of 70? How does the prevalence of asthma and COPD in Australia compare with that in other countries? WHAT WE NEED TO DO: Conduct community-based studies examining the burden of illness due to obstructive lung disease, using a common protocol that allows international comparisons of data.