An ArcView extension, GeoVR, has been developed to facilitate interactive creation of 3D Virtual Reality Modeling Language (VRML) models from existing 2D Geographical Information System GIS data on top of ArcView Internet Map Server (IMS) and 3D Analyst. This extension is primarily a server program, which can offer both 2D and 3D visualization services. By providing several parameters such as base height, offset height, vertical exaggeration factor, etc. in an HTML form, a 3D scene can be created on the fly. Then, the 3D scene is transferred into a VRML representation automatically, and is delivered to the client through the Internet. The GeoVR effort demonstrates how to adapt existing GIS functionalities to the increasingly popular Web environment by using ArcView IMS and Avenue. Key Words: Geographical Information System, Virtual Reality, Virtual Reality Modeling Language, World Wide Web, Client/Server, GeoVR