HAZDIG (HAZardous DIspersion of Gases) is a user-friendly PC-based software for generating scenarios for the emissions and gaseous dispersion of hazardous chemicals. It can simulate accidental as well as normal release but has been specifically developed as a tool for studying accidental release of hazardous chemicals and the consequences. HAZDIG is made-up of five main modules-data, release scenario generation, dispersion, characteristics estimation, and graphics. HAZDIG incorporates the latest models for estimating atmospheric; stability and dispersion. The data needed to run the models is easy to obtain and feed-properties of chemicals, operating conditions, ambient temperature, and a few commonly available meteorological parameters. A database containing various proportionality constants and complex empirical data has been built into the system. The graphics module enhances the user friendliness of the software, and enables presentation of the results in an easy-to-understand and visually appealing manner. The output of the software is formatted so that it can be directly used for reporting the results without the need of editing.