The authors explored whether a new pedagogy using personal response systems (clickers) along with case study teaching improved students' perceptions of their understanding of science in large introductory biology classrooms. Twelve faculty from nine institutions and 1,457 students across the United States and Canada participated in this study. Faculty taught six to eight topics in biology by lecture or clicker case method, alternating the methods within the same course. Data include student responses to a survey questionnaire. Results indicated that students, especially women and nonscience majors, were generally positive toward the use of both clickers and cases. (Contains 3 tables.)