Since 1979, the U.S. Army Research Laboratory has been developing and distributing the BRL-CAD constructive solid geometry (CSG) modeling package for a wide range of military and industrial applications. The package includes a large collection of tools and utilities including an interactive geometry editor, ray-tracing and generic frame buffer libraries, a network-distributed image-processing and signal-processing capability, and an embedded scripting language. As part of this effort, a multivolume tutorial series is being developed to assist users in the many features of the BRL-CAD package. The "Introduction to MGED," which is the second volume in the series, is intended to provide new users with a basic understanding of the Multi-Device Geometry Editor (MGED), which is the heart of BRL-CAD. Other volumes focus on installation procedures, advanced features, and programming. Army Research Laboratory, ARL-SR-102.