— This paper describes a variety of methods that can be used to create realistic, random 3D environments for serious games requiring real-time performance. These include the generation of terrain, vegetation and building structures. An interactive flight simulator has been created as proof of concept. An initial evaluation with two small samples of users (remote and hallway) revealed some usability issues but also showed that overall the flight simulator is enjoyable and appears realistic and believable. Keywords – serious games; 3D terrain modeling; computer graphics; flight simulator.