The computer model is a multiple point source code with terrain adjustment. The model specifications for testing were suggested by team 'B' on complex terrain at the Regional Workshop on Air Quality Modeling in Chicago, February 1980. It is a sequential model utilizing hourly meteorological input. It assumes a normal distribution in the vertical and a uniform distribution across a 22.5 degree sector. The initial screening technique for complex terrain applications, described in the Guideline on Air Quality Models (revised), has been incorporated as an option in COMPLEX1.