An important reason for controlling air pollutants such as particulate matter or sulfur dioxide is the damaging effects they have on human health. These effects include premature death as well as increases in the incidence of chronic heart and lung disease. Estimates of the health damages associated with air pollution are important because they can provide both an impetus for environmental controls and a means of evaluating the benefits of specific pollution control policies. To estimate the health damages associated with air pollution in developing countries, policy makers are often forced to extrapolate results from studies conducted in industrialized countries. These extrapolations, however, may be inappropriate for two reasons. First, it is not clear that the relationships found between pollution and health at the relatively low levels of pollution experienced in industrialized countries hold for the extremely high pollution levels witnessed in developing countries. Levels of particulate matter, for instance, are often three to four times higher in developing countries than in industrialized ones. Second, in developing countries, people die at younger ages and from different causes than do people in industrialized countries, implying that extrapolations of the impacts of air pollution on mortality may be especially misleading. This paper reports the results of a study relating levels of particulate matter to daily deaths in Delhi, India, between 1991 and 1994. We focus on Delhi, the capital of India, because it is one of the world's most polluted cities. Between 1991 and 1994, the average total suspended particulate (TSP) level in Delhi was 375 micrograms per cubic meter-approximately five times the annual average standard of the World Health Organization (WHO). Levels of TSP in Delhi during this time period exceeded WHO's twenty-four-hour standard on 97% of all days on which readings were taken. Although particulate matter-produced by motor vehicles, smelters, the burning of refuse, and two coal-fired power plants-is Delhi's main air pollution problem, levels of sulfur dioxide (SO2) and oxides of nitrogen (NOx) are below U.S. limits.