This study stemmed from concerns among researchers that reform efforts grounded in promoting inquiry as the basis for teaching science have not achieved the desired changes in American science classrooms. Many science teachers assume that they are employing inquiry-based strategies when they use cookbook investigations with highly structured step-by-step instructions. Additionally, most science teachers equate hands-on activities with classroom inquiry and, as such, repeatedly use prepackaged, disconnected activities to break the monotony of direct instruction. Despite participation in numerous professional development activities, many science teachers continue to hold misconceptions about inquiry that influence the way they design and enact instruction. To date, there is very limited research exploring the role of inquiry-based professional development in facilitating desired changes in science teachers' conceptions of inquiry. This qualitative study of five high school science teachers explores the ways in which authentic inquiry experiences with a team of scientists in Panama shaped their conceptions and reported enactments of inquiry-based instruction. Our findings suggest that professional development experiences engaging science teachers in authentic research with scientists have the potential to change teachers' naïve conceptions of inquiry, provided that necessary supports are provided for reflection and lesson design.