This study, suggested by an EPA Regional Workshop in February 1980, was conducted as a simple analysis to investigate whether or not a sequential air quality simulation model, capable of accepting onsite hourly meteorological data, could be recommended as a screening model for estimating worst-case pollutant impacts on complex terrain. The study intercompared the highest 24-h average pollutant concentration values obtained using four algorithmic air quality simulation models: Complex I, Complex II, Valley, and Valley-BID. The authors conclude that the Valley-BID (or pencil and paper calculations using the same assumptions) are most appropriate for screening analyses for maximum 24-h concentrations resulting from plume impaction on terrain near the height of an elevated stabilized plume.