Chronic obstructive pulmonary disease (COPD) is a very common lung disease most often related to a history of smoking. It becomes more prevalent with increasing age but remains under-diagnosed and under-treated in the elderly population. The Global Initiative for Obstructive Lung Disease (GOLD) programme has been instrumental in providing standard diagnostic criteria as well as recommendations for prevention and management of COPD. GOLD recommendations define COPD as a post-bronchodilator forced expiratory volume in 1 second (FEV(1))/forced vital capacity (FVC) of <70%, with the severity based on the value of FEV(1). This recommendation is different from that of many previous reports that have recommended diagnosing obstruction using the statistically derived lower limit of normal (LLN), which varies for each person according to age, height, ethnicity and gender. While the use of a 70% ratio may be simpler, it may result in under-diagnosis of airflow obstruction in younger people and over-diagnosis in the elderly. This is particularly important as the elderly may be most sensitive to many of the adverse effects of medications used in the treatment of COPD, including corticosteroids and anticholinergic bronchodilators.Most of the studies comparing the LLN and a fixed ratio of 70% have not been performed with post-bronchodilator testing as recommended by GOLD. Generation of post-bronchodilator reference sets and studies comparing the LLN with the post-bronchodilator FEV(1)/FVC ratio of <70% will help resolve this issue. One recent study examined patients admitted to hospitals who had an FEV(1)/FVC ratio of <70% but above the LLN, and found they were at increased risk of death and COPD complications. This would support the use of GOLD criteria. Further studies examining this population are needed.In addition to the uncertainties about what diagnostic criteria should be utilized for diagnosis of airflow obstruction, different organizations make different recommendations on screening spirometry. A conservative recommendation is to perform spirometry in symptomatic individuals. It is important to remember that while COPD is under-diagnosed in the elderly, this group is also at a higher risk of being falsely classified as having airflow obstruction using the 70% ratio recommended by GOLD. This can result in unnecessary use of medications and increased risk of adverse effects to which the elderly are more prone.