The methods of virtual reality (VR) will come to play a routine part in the work of hospitals. It is difficult to understand and explain what VR means in medicine and its scope in medicine. This paper distinguishes the four functional categories of Immersive VR, Desktop VR, Pseudo VR and Inverse VR. Immersive VR uses a head-mounted display and data gloves as input devices, while Desktop VR uses VR shutter glasses and a 3D input device such as the 3D mouse. Pseudo VR comprises interactive controllable animation. Inverse VR uses, for example, biosignals as an input device in order to support the computer user in the real world. This paper discusses the potential applications of the four categories of VR in medicine with reference to topical projects.