Science education research on nature of science (NOS) has mostly focused students’ and teachers’ views of NOS, while less attention has been paid to the appropriateness of various NOS aspects at different levels in the educational system. Even more scarce is research focusing teachers’ perspectives on these matters. The aim of this study is to: 1) analyze NOS progression in the Swedish national curriculum, and 2) investigate science teachers’ perspectives on a NOS progression for year 1-9. Participants in the study are Swedish in-service science teachers (grades 1-9) who took part in a three-year research-project focusing NOS teaching. Throughout the project the teachers met in focus-group discussions. They also planned and implemented NOS lessons in their classrooms. Sources of data are: 1) curriculum material, and 2) two focus groups meetings about NOS progression (recorded and transcribed). The results show that many NOS aspects are, at least implicitly, part of the Swedish curriculum, but no specific progression is described. The teachers’ suggestions for NOS progression are based on arguments concerning the level of abstractness. Theoretical approaches and unfamiliar contexts are considered abstract, while hands-on activities, everyday contexts, and historical cases are considered concrete approaches to NOS.