A much more attractive way to use the internet was discovered. Users are represented by avatars in the fantasy persistent 3D world, and the avatars apparently come to occupy a special place in the hearts of their creators (Castronova, 2001). At present, millions of people worldwide have accounts to some kind of virtual environments. Virtual world may soon become the primary venue for all online activities (Castronova, 2001) including learning. Imagine that one can gain knowledge and skills by social interactions in virtual worlds. A massively multi-student online learning environment (MMOLE) is a pedagogically designed space where students would spend much time learning online by doing and interacting with others. Furthermore, massively multiplayer online games (MMOGs) or massively multiplayer online role playing games (MMORPGs) allow individuals, through their avatars, to learn in the service of games goals and through problem solving and collaboration. This article aims at exploring the pedagogical potentials of virtual worlds. The strengths and weaknesses will be outlined and some of the issues will be discussed through case studies. Hopefully, lessons can be learned and the future virtual worlds can become a more powerful and effective environment to engage students in learning.