Epidemiological studies conducted in a number of countries have consistently demonstrated associations between concentrations of ambient air pollution and adverse health outcomes, including premature mortality, cardiorespiratory hospitalizations, emergency department visits for respiratory diseases, asthma attacks, respiratory symptoms, and restricted activity. These associations have prompted regulatory agencies in several countries, including Canada, to either revise current air quality standards or establish new ambient guidelines. In this article, recent epidemiological research in Canada is briefly reviewed in relation to the establishment of PM 10 and PM 2.5 national air quality objectives. Economic approaches to evaluating costs and health benefits of controlling air pollutants are discussed, and their use illustrated in evaluating the consequences of reducing the sulphur content of gasoline. Ongoing epidemiological research on the health effects of air pollution is outlined, and strategies for evaluating and managing the health risks of air pollution examined.