This article presents the foundation of research around which other contributions in this issue are structured. It follows from a larger study aimed at supporting the professional development of beginning teachers with respect to their personal epistemology. The study explores the link between beliefs and practices in continuing education.It is an avenue that is still little used in research, particularly in Quebec, where research has focused more often on pre-service teachers. Previous studies identified highlight inconsistencies between expressed beliefs (epistemological and (...) pedagogical) and actual teaching practices. These concepts that are central to our approach. They will be clarified and illustrated in this article with the help of portraits of two high school natural science (NS) teachers offering a particular look at the tensions present in the belief-practice articulations. These two portraits are elaborated mostly from qualitative data drawn from explanatory interviews, from which similarities and dissimilarities emerge with regard to the question studied. The article conclude with suggestions for accompanying beginning teachers in resolving these tensions. (shrink)