The Complex Terrain Model Development (CTDM) project has met its original objectives of producing an atmospheric dispersion model appropriate to elevated sources of air pollutants located in mountainous terrain settings under stable atmospheric conditions. The model development effort has focused on predicting concentrations during stable atmospheric conditions, which have generally been associated with the highest ground surface values. The program, initiated in June 1980, has involved the performance of four major field experiments which produced data for model development and verification purposes, and a complete model. The CTDM which has been developed and tested in the program is an advanced Gaussian model that uses a flow algorithm which provides plume trajectories and deformation information. CTDM requires substantially more information on terrain and local meteorology than prior complex terrain models. It can be used with simpler data bases, but demonstates degraded performance under these circumstances.