This study evaluated preservice teachers' professional-knowledge transformation while they participated in simulated professional-development activities via a "Second Life" virtual classroom--an Internet-based multiuser virtual environment (MUVE). While a cohort of preservice teachers experienced the MUVE environment, the instrumental exploratory case study highlighted how 2 preservice teachers among the 12 internalized professional knowledge, as well as how that knowledge transferred into active teaching practice. The study was framed around sociocultural theory as it pertains to enabling intramental functioning through co-constructed activities. The preservice teachers' debriefings and reflective statements suggest that they entered the Zone of Proximal Development (ZPD)--the range of potential an individual has for learning, with that learning being shaped by the social environment--indicating the positive potential of using an MUVE to promote self-regulatory pedagogic behaviors. (Contains 6 figures and 2 footnotes.)