This NTIS tape contains 9 files. The following atmospheric dispersion models are made available on this tape. (1) PAL version 80080 is an update of version 78310. PAL is a method of estimating short-term dispersion using Gaussian-Plume steady-state assumptions for Point, Areas, and Line Sources. (2) HIWAY-2 version 80080 is an update to the HIWAY model. This steady-state Gaussian model can be applied to determine air pollution concentrations downwind of 'at-grade' and 'cut-section' highways. (3) TEM8 is a Fortran program designed to predict ground level, short-term concentrations of atmospheric pollutants from point and area sources. (4-6) MESOPLUME, MESOPUFF, and MESOGRID are three variable-trajectory regional-scale atmospheric dispersion models. They are designed to simulate the air quality impacts of multiple point sources at long transport distances. MESOPLUME and MESOPUFF are Gaussian dispersion models while MESOGRID is a grid model, based on the Egan-Mahoney method of moments. T he three remaining files are: MESOPAC, a meteorological preprocessor program. MESOFILE, a postprocessing system designed for file management, file merging, file manipulations, statistical analyses, and graphical display. MESOTEST, an example data base for the MESOPLUME, MESOPUFF and MESOGRID dispersion models...Software Description: The system is written in the Fortran programming language for implementation on an UNIVAC computer using the 33R operating system. 7K bytes of core storage for HIWAY-2, 92K for MESOGRID are required to operate the system.