Epidemiological studies have revealed strong associations between exposure to particulate matter and adverse health effects. Effects arising from both chronic and acute exposure have been found, although the underlying pathophysiological mechanisms remain poorly understood. Studies within this research area are investigating the cardiovascular and respiratory effects of aerosol inhalation. Markers of autonomic dysfunction, systemic inflammation and endothelial activation are being examined through both in vivo and in vitro methodologies. The physiological responses of healthy individuals, and those from susceptible populations, are being investigated through controlled exposures to concentrated ambient particulate of known chemical and physical characteristics. An understanding of the relationship between aerosol characteristics and cardiac and pulmonary effects is essential for developing appropriate and effective air quality exposure standards and emission regulations.