ABSTRACT:The research literature is just beginning to uncover factors involved in sustaining constructivist learning environments, such as Project-Based Learning (PBL). Our case study investigates teacher responses to the challenges of constructivist environments, since teachers can play strong roles in supporting or undermining even the best constructivist environments or materials. We were invited to work as mediators with a middle-school science staff that was experiencing conflicts regarding two learning environments, PBL (which was the school's "politically correct" learning environment) and traditional. With mediated group workshops, teachers were sensitized to their own and colleagues' individual learning differences (ILDs), as measured by two styles inventories (the LSI-Kolb, 1976; and the LCI-Johnston & Dainton, 1997). Using these inventories, a learning-environment questionnaire, field notes, and delayed interviews a year later, we found that there was a relationship between teachers' preferred styles, epistemological beliefs, and their preferred teaching environment. Moreover, when the participating teachers, including early-adopters and nonvolunteers to PBL, became more sensitive to their colleagues' preferences, many staff conflicts were resolved and some mismatched teachers expressed more openness to PBL. We argue that having teachers understand their own ILDs and related responses to constructivist learning environments can contribute to resolving staff conflicts and sustaining such environments. We present a cognitive model and a strategy which illustrate this argument.C