Ciudad Juárez, Chihuahua, is home to the U.S.–Mexico border’s largest maquiladora labor force,and also its worst air pollution. We marshal two types of evidence to examine the link betweenmaquiladoras and air pollution in Ciudad Juárez, and in its sister city, El Paso, Texas. First, we use apublicly available sector-level emissions inventory for Ciudad Juárez to determine the importance of allindustrial facilities (including maquiladoras) as a source of air pollution. Second, we use original plantleveldata from two sample maquiladoras to better understand the impacts of maquiladora air pollution onhuman health. We use a series of computational models to estimate health damages attributable to airpollution from these plants, we compare these damages to estimates of damages from non-maquiladoraindustrial polluters, and we use regression analysis to determine whether the poor sufferdisproportionately from maquiladora air pollution. We find that air pollution from maquiladoras hasserious consequences for human health, including respiratory disease and premature mortality. However,maquiladoras are clearly not the leading cause of air pollution in Ciudad Juárez and El Paso. Moreover,most maquiladoras are probably less important sources of dangerous air pollution than at least onenotoriously polluting Mexican-owned industry. Finally, we find no evidence to suggest that maquiladoraair pollution affects the poor disproportionately.