To define how the « What to Teach » is determined in an educational context where the program permits the teacher a large margin of manoeuvre, this article presents the findings of a study on the relation between Geography teachers in colleges and the choice of subject content taught. The objective is to understand how teachers choose their content and, in so doing, contribute to the construction of Geography as an educational discipline. Two types of data were analysed. An examination of the documents produced during the period of the Human Sciences program reform (1985-1990) by the Pedagogical Comittee for Geography permits us to trace the collective process in the elaboration of Ministry guidelines. The analysis of teaching discourse, based on partially directed interviews with twelve Geography teachers, leads us to posit an organisational matrix for the meaning of subject content. The teachers weave together the main idea of their course by juxtaposing their conception within a dynamic of tensions between creativity and norms, certainty and doubt, personal culture and Geographic referential.