An econometric model of air pollution for an intraurban location (the Chicago area) is constructed and estimated. The model treats employment and population as simultaneously determined. Exogenous variables are selected to represent transportation infrastructure investments resulting primarily from federal and state decisions. The exogenous variables account for the relative services provided by highways, commuter railroads, rail rapid transit, waterways, and airports. The employment location equations appear to be considerably more successful than those in previous studies. These equations indicate that waterway availability constrains the locational options of most major industrial air polluters; that highway accessibility is a more influential factor in industrial than services location choices; that rail rapid transit accessibility is more important to services than industrial locations; and that major airports attract light industrial development. The success of the employment location equations reflects the importance of disaggregating intraurban modes of transport and of adding to urban location models the local effects of interurban modes of transport such as water and air.