An emerging technology, classroom communication systems (CCSs), has the potential to transform the way we teach science in large-lecture settings. CCSs can serve as catalysts for creating a more interactive, student-centered classroom in the lecture hall, thereby allowing students to become more actively involved in constructing and using knowledge. CCSs not only make it easier to engage students in learning activities during lecture, but also enhance the communication among students, and between the students and the instructor. This enhanced communication assists the students and the instructor in assessing understanding during class time, and affords the instructor the opportunity to devise instructional interventions that target students' needs as they arise. By facilitating a shift from a passive, teacher- centered (i.e., lecture-style) classroom, toward an interactive, student-centered classroom, a CCS helps to create a classroom environment that accommodates a wider variety of student learning styles, making the learning of science a much more positive experience for students. CCSs are unique tools that teachers can use for facilitating learning and for improving students' attitudes toward science. This article describes our experiences over the last seven years using a CCS called Classtalk to teach eight different introductory-level physics courses at the University of Massachusetts in Amherst. This system has also been used in introductory courses in biology, economics, and sociology. (Contains 55 references.) (Author/MM)