Web3D open standards allow the delivery of interactive 3D virtual learning environments through the Internet, reaching potentially large numbers of learners worldwide, at any time. This paper introduces the educational use of virtual reality based on Web3D technologies. After briefly presenting the main Web3D technologies, we summarize the pedagogical basis that motivate their exploitation in the context of education and highlight their interesting features. We outline the main positive and negative results obtained so far, and point out some of the current research directions.