Inflammation provides a potential mechanistic link between inhalation of particles and the diverse health effects found in epidemiologic studies. Considerable uncertainty remains as to the importance of the inflammation in mediating these effects and where that inflammation is occurring: lung, vascular endothelium, or distant organs, including the heart. This article briefly reviews the role of inflammation in pulmonary and cardiovascular disease and explores the evidence that the health effects of PM exposure are mediated, at least in part, by inflammation.