This report is the latest in HEI's program of studies to assess the health impacts of air quality actions. Research Report 148 describes a study to evaluate the effect of a short-term, temporary intervention to reduce traffic congestion during the 1996 Summer Olympic Games in Atlanta, Georgia. A previous study had shown a decrease in acute care visits for pediatric asthma and a concomitant decrease in concentrations of ozone, particulate matter, and carbon monoxide.