We estimate the effect of short-term air pollution exposure (PM 2.5 and ozone) on several categories of crime, with a particular emphasis on aggressive behavior. To identify this relationship, we combine detailed daily data on crime, air pollution, and weather for an eight-year period across the United States. Our primary identification strategy employs extremely high dimensional fixed effects and we perform a series of robustness checks to address confounding variation between temperature and air pollution. We find a robust positive effect of increased air pollution on violent crimes, and specifically assaults, but no relationship between increases in air pollution and property crimes. The effects are present in and out of the home, at levels well below Ambient Air Pollution Standards, and PM 2.5 effects are strongest at lower temperatures. The results suggest that a 10% reduction in daily PM 2.5 and ozone could save $1.4 billion in crime costs per year, a previously overlooked cost associated with pollution.