In this study we sought to understand factors that shaped teachers' use of student inquiry projects. We examined, over 3 years, the practices and conceptions of two teachers involved in implementing student inquiry projects. Neither teacher was initially satisfied with her success at supporting student inquiry, but the two had very different responses to difficulties they faced. These responses related strongly to their ideas about how learning should be structured. There was less relation between their stated views about the nature of science and their use of inquiry than was expected. The teacher with espoused views about the nature of science generally in accord with reform documents did not support student inquiry projects that involved actual investigations. The teacher with views on the nature of science less aligned with reform documents worked hard to support student investigations in her classroom. Our findings support the claim that merely learning about the nature of science or about student inquiry may not generate changes in a teacher's practice. On closer analysis, we found that the two teachers understood aspects of the nature of science from two quite different perspectives, the proximal and the distal. The proximal view of the nature of science was more closely aligned with implementation of actual student investigations. The efforts of these two teachers in implementing inquiry illustrate the dilemmas and challenges they faced as they attempted student inquiry projects. (Contains 3 tables.)