Multi-User Virtual Environments (MUVEs) are computer-generated worlds represented in 2D or 3D to which users connect over the Internet. Users choose a computer-generated character, called an avatar, to represent themselves within this environment and can then move this avatar around the world. Other users do the same from other locations, and then interact with each other within this environment. A list on the Virtual Worlds Review website (2007) lists 28 current MUVEs. This article focuses on the use of Second Life in learning and teaching, since this is the environment used in the projects with which the author has been involved, however the principle of virtual presence and how this supports interaction, applies to MUVEs in general.