There are now more than 150 published epidemiologic studies of health effects of particulate air pollution and dozens of related literature reviews. This article explores the basic inferences currently being drawn from the literature regarding the epidemiologic evidence particulate pollution induced health effects. Although there is not a complete consensus of opinion, most reviewers conclude that the overall epidemiologic evidence suggests that particulate air pollution, especially fine combustion-source pollution common to many urban and industrial environments, is an important risk factor for cardiopulmonary disease and mortality. Most of the epidemiological effort has focused on effects of acute exposure, but effects of chronic exposure may be more important in terms of overall public health relevance. Some reviewers contend that long-term, repeated exposure likely increases the risk of chronic respiratory disease and the risk of cardiorespiratory mortality. There is more general (but still not unanimous) agreement that short-term exposures to particulate pollution can exacerbate existing cardiovascular and pulmonary disease and increase the number of persons in a population who become symptomatic, require medical attention, or die.