Estimating the effects of wind-blown dust on aerosol concentrations in semi-arid areas of the southwestern United States is crucial for defining the extent of human exposure to suspended particulates, as well as differentiating natural versus anthropogenic contributions to PM2.5 and PM10 concentrations. Here we present results of a high-spatial-resolution CMAQ modeling study for the Las Vegas region for the summer months of the year 2000. The model dynamics over the Las Vegas region were derived from mesoscale model (MM5, Version 3.4) runs with grid resolutions of (1) 1.3 km in an inner domain approximately 100 km on a side and (2) 12 km in a larger outer domain. The mesoscale model runs employed gridded four-dimensional data assimilation (FDDA) in the coarse-resolution outer domain and surface observational FDDA over the fine-resolution inner domain. The observational wind velocity data set was obtained at 12 monitoring sites in and around the Las Vegas metropolitan area. Wind-blown dust emissions were estimated by using high-spatial-resolution land use data sets, emission algorithms derived from limited field observations during the study, and micrometeorological results from the MM5 model. Several simulations conducted with the CMAQ model, using these emissions and MM5-derived dynamics, evaluated the effect of wind-blown dust on aerosol loading at selected monitoring sites in the study region. Results from the calculations will be presented, and the sensitivity of the aerosol loadings at the monitoring sites to wind-blown dust will be discussed.