Inquiry is seen as central to the reform of science teaching and learning, but few teachers have experience with scientific inquiry and thus possess very naive conceptions of it. One promising form of professional development, research experiences for teachers (RETs), allows teachers to experience scientific inquiry in the hopes that these experiences will then translate to inquiry in the classroom. As intuitively pleasing as these programs are, scant evidence documents their effectiveness. For this study, four secondary science teachers were followed back to their classrooms following a 6-week, marine ecology RET. The research employed qualitative and quantitative data collection to answer these questions: What were the teachers' initial conceptions and enactment of classroom inquiry, and how did they change after the RET?; How did changes in the nature and use of questions highlight changes in inquiry enactment?; and How were the teachers' changes linked to the RET and are there changes that cannot be explained by the RET experience? Teachers who entered the program with more sophisticated, theory-based understanding of teaching and learning were more apt to understand inquiry as a model and to use classroom-based inquiry throughout their teaching following the program. Implications for professional development are discussed. (Contains 1 figure and 8 tables.)