After 17 years of prototyping, a first release version of the St Mark's Hospital teaching simulator is in final preparation. Advances in computer processing power and graphics cards make it possible to achieve real-time processing of colon and endoscope characteristics and a simulated endoscopic view at an acceptable cost. Realistic feel or "force feedback" for all instrument controls and shaft movements is incorporated. To make the simulator more than a "video game", a package of teaching and assessment features is to be incorporated, including interactive animated graphics to explain particular endoscope loops and situations and the variations of colonic anatomy that are typically encountered. Simulation should spare patients from being used for the early phases of training and should speed up and quantify the learning process. Simulators may introduce even experienced endoscopists to some of the advanced options available in current or future endoscopes or accessories, as well as the use of imminent new technology such as the magnetic imaging system.