The Complex Terrain Dispersion Model (CTDMPLUS), a point-source, steady-state, model for complex terrain applications, is described. The model is unique in the manner in which it simulates the flow and plume distortion near fully defined three-dimensional terrain. Emphasis is given to windward side impacts. Simplicity is maintained by applying flow distortion corrections to flat-terrain, Gaussian and bi-Gaussian pollutant dstributions. The algorithms for stable and neutral conditions are based on the well established concept of a dividing streamline. These algorithms have been developed with the use of data from three major plume-impaction field studies and a number of fluid modeling studies. The algorithms for plumes released into convective layers are based on recent understanding of the convective boundary layer through fluid modeling, numerical modeling, and field studies. The non-Gaussian nature of vertical dispersion is accounted for; lateral dispersion is modeled with the aid of convective scaling concepts.