The MESOscale FILE management and analysis package (MESOFILE) is a highly flexible postprocessing system designed especially for interface with the MESOPLUME, MESOPUFF, and MESOGRID regional-scale air quality models, and the MESOPAC meteorology package. The MESOFILE package is composed of five distinct program modules consisting of file management, file merging, file manipulation, statistical analysis, and graphical display. The file management system automatically catalogues input parameter values and output file locations of all regional-scale model simulations; any set of regional-scale model output can, therefore, be easily accessed for postanalysis. Postprocessing capabilities include multiple file averaging, multiple file addition, point-by-point and bulk statistical comparison of two files, contour plots of concentration and most meteorological fields, and vector plots of wind fields.