The elderly are frequently classified as being particularly susceptible to air pollution. The basis of this increased sensitivity is not known but it is likely that it is linked to age-related impaired function of the lung. However, given this uncertainty and increased impact of air pollution of this section of the community there is a need to explore the mechanisms involved. Gaseous air pollutants such as ozone and nitrogen dioxide, or many of the components adsorbed onto the surface of respirable particles, are either powerful oxidants or capable of generating free radicals. If unabated, oxidants can cause injury to the delicate cells that line the respiratory tract. Small molecular weight antioxidant defences present in respiratory tract lining fluid (RTLF) represent the first line of defence against a range of oxidants that enter the lung. The quantity and quality of the RTLF airways antioxidant network are, therefore, likely to be important determinants of the impact of the oxidant challenge on the underlying respiratory epithelium. As yet, comprehensive information on the distribution and variability of respiratory tract lining fluid antioxidant defences is only available in young, mainly healthy volunteers. Studies undertaken in patients with a range of respiratory diseases suggest that marked changes in the distribution of respiratory tract lining fluid antioxidants can occur. Information is not currently available on the impact of ageing on the respiratory tract lining fluid antioxidant defence network. As several respiratory tract lining fluid antioxidants are of dietary origin, the elderly, who often have different dietary patterns to younger individuals, may have decreased availability of important antioxidants. Given these possibilities, a better understanding of respiratory tract lining fluid antioxidant defences in the aged lung is warranted.