In this paper, we review past empirical research studies on the use of three-dimensional immersive virtual worlds in education settings such as K-12 and higher education. Three questions guided our review: (1) How are virtual worlds (eg, "Active Worlds", "Second Life") used by students and teachers? (2) What types of research methods have been applied? (3) What research topics have been conducted on virtual worlds in teaching and learning, as well as their related findings? Overall, we found that virtual worlds may be utilised for the following uses: (1) communication spaces, (2) simulation of space (spatial), and (3) experiential spaces ("acting" on the world). Most of the studies reviewed were descriptive and conducted in polytechnic and university settings, and past virtual world research had been most frequently carried out in the media arts and health and environment disciplines. Three main research topics were found: participants' affective domain, learning outcomes and social interaction. We conclude by summarising some major findings and discussing three limitations of previous empirical studies. Several recommendations for future research related to virtual worlds in education settings are also provided.