Models-3 is a flexible software system designed to simplify the development and use of air quality models and other environmental decision support tools. It is designed for applications ranging from regulatory and policy analysis to understanding the complex interactions of atmospheric chemistry and physics. The June 2000 release of Models-3 contains a Community Multi-Scale Air Quality (CMAQ) modeling system for urban to regional scale air quality simulation of tropospheric ozone, acid deposition, visibility, and fine particles. The principal feature of this release is the ability to install and run Models-3 on a stand-alone Windows-NT based computer. This Installation Manual includes an overview of the installation process, system requirements, procedures for installation of Models-3, and a description of system administration functions.