This article describes the development of a questionnaire to discover primary school students' perceptions of science, religion and the relationships between them on a range of topics that are known as Big Questions. The questionnaire was administered in 16 primary schools in England with over 750 students aged 10-11. The findings indicate that students in this age group have begun to consider how science and religion relate and that while there is a diversity of positions, a significant proportion perceived science and religion to conflict. Analysis of responses also indicated that primary school students' epistemic insight was limited in relation to their understanding of the nature of science and, in particular, the idea that science has limitations. The basis and potential consequences of such views are considered and recommendations for teaching practice are presented, together with ideas for future research. It is anticipated that the study will inform teachers and curriculum planners developing approaches and guidance materials in science and religious education.