There is wide interest in the educational and motivational use of games and virtual worlds, but evidence is often lacking. We are researching several important questions in this area. What do people learn from playing games? Can we design playful, challenging learning experiences? What is it like to teach in a virtual world? How do people participate and express themselves in these contexts? How should these experiences be integrated with other forms of learning and teaching? Such questions are explored in relation to settings as diverse as packages developed for curriculum areas like mathematics through to commercial massively-multiplayer online games.