Public housing developments across the United States are being demolished, potentially increasing local concentrations of particulate matter (PM) in communities with high burdens of severe asthma. Little is known about the impact of demolition on local air quality. At three public housing developments in Chicago, IL, PM with an aerodynamic diameter Ͻ10 m (PM 10 ) and Ͻ2.5 m were measured before and during high-rise demolition. Additionally, size-selective sampling and real-time monitoring were concurrently performed upwind and downwind of one demolition site. The concentration of particulates attributable to demolition was estimated after accounting for background urban air pollution. Particle microscopy was performed on a small number of samples. Substantial increases of PM 10 occurred during demolition, with the magnitude of that increase varying based on sampler distance, wind direction, and averaging time. During structural demolition, local concentrations of PM 10 42 m downwind of a demolition site increased 4-to 9-fold above upwind concentrations (6-hr averaging time). After adjusting for background PM 10 , the presence of dusty conditions was associated with a 74% increase in PM 10 100 m downwind of demolition sites (24-hr averaging times). During structural demolition, short-term peaks in real-time PM 10 (30-sec averaging time) occasionally exceeded 500 g/m 3 . The median particle size downwind of a demolition site (17.3 m) was significantly larger than background (3 m). Specific activities are associated with realtime particulate measures. Microscopy did not identify asbestos or high concentrations of mold spores. In conclusion, individuals living near sites of public housing demolition are at risk for exposure to high particulate concentrations. This increase is characterized by relatively large particles and high short-term peaks in PM concentration.