In this paper, the general principles and practices adopted as guidelines to a graduate course for secondary mathematics teachers are discussed. It is argued that once the curriculum is designed both to complement the teachers' subject content knowledge and to provide activities promoting links between their conceptual knowledge and their actual practices, it can have a strong positive influence in teachers' subsequent practices. Two teachers who completed the course were subsequently followed during a two year period. They were interviewed and their practices were observed. Their reflections on the main differences in their practices before and after attending the course are analyzed. (Author/NB)