The aim of this article is to examine Swedish principals’ conception of their leadership role when realising research-based teaching in relation to research traditions. The study is based on ten principals’ conceptions of research-based teaching, analysed phenomenographically. The results indicate that application of research results is in several respects the most dominant notion of what teaching on a scientific basis entails. The conceptions of the principals’ derive from traditionally accepted beliefs and expectations, which is in line with how national reforms are implemented. Instructional and transformational leadership models are represented when leading schools toward research-based teaching