The effect of teachers’ beliefs about the nature of science on their classroom practice was exam ined. Three science teachers were interviewed to elucidate their understanding of science and science teaching. To make connections between their thinking about science and their actions in teaching science, each teacher's classes were observed for at least 35 hours. The teachers differed in their views of the nature of scientific theories, scientific processes, and the progression and change of scientific knowledge. Teachers’ beliefs about science influenced not only explicit lessons about the nature of science, but also shaped an implicit curriculum concerning the nature of scientific knowledge. © 1990, Sage Publications. All rights reserved.