Personal response systems (PRS)--also called student response systems (SRS), or more commonly, "clickers"--can be a catalyst for transformation of a learning environment from one of silence to one rich in dialogue and interaction. But how is this transformation achieved? In this paper, we present three case studies of instructors who use PRS in undergraduate science and math classes at a research-intensive institution in the Midwest, USA. All three instructors reported having to make significant adjustments to their teaching over time in order to transform their respective learning environments and fully realize the benefits of PRS. These adjustments included (1) modifying activities to overcome the tension between the students' desire for anonymity and the need for interactivity to enhance learning, and (2) revising PRS questions in response to student behavior. We contend that transformation of the environment with PRS is neither instantaneous nor straightforward. As such, faculty who introduce PRS to their classrooms may benefit from substantial pedagogical and technological support. Finally, we note that the ongoing feedback about student learning in the classroom that PRS provides may act as a powerful catalyst to transform faculty, moving them from teacher-centered conceptions and approaches to teaching to student-centered conceptions and approaches. (Contains 1 table and 1 figure.)