The aim was to describe both the overall and specific operational characteristics of the computer programs which embody the model. An airshed simulation package consisting of four computer programs was developed. Three of the programs are subsidiary to the main program which is used to predict ground level pollutant concentrations. The main objective is to explain the basic computational structure of the package, indicating the function of all programs. To illustrate the manner in which a typical airshed simulation is performed, the step-by-step application of each program is described, discussing required inputs, calculations performed, and use of the program output. A detailed description of the individual programs is presented, focusing on objectives, structure and capabilities. A complete set of instructions is presented for the use of all programs. Computing system information is given, including program size, computing time, and hardware requirements. A set of tables is presented depicting the data-deck setup for every program. The tables include a detailed description of the input parameters, their units, and the format of each card. Listings of all programs are also provided. A symbol glossary and several typical examples of program output are included.