Simulation results from three global-scale models of atmospheric mercury have been used to define three sets of initial condition and boundary condition (IC/BC) data for regional-scale model simulations over North America using the Community Multi-scale Air Quality (CMAQ) model. The IC/BC data sets derived from these global models show significant differences in air concentration of mercury species. Variations in the CMAQ model simulation results obtained from each of the three IC/BC data sets provide a measure of the range of certainty regarding patterns of mercury deposition across the study region and the relative importance of domestic versus foreign emission sources responsible for these deposition patterns.