This article examines how curriculum studies can inform training and development programs for museum teachers (docents, interpreters, guides, gallery educators, and so on). It focuses on the results of a year-long study done with eight museum teachers in three Canadian informal learning settings. A key aim of this research was to examine the question of how museum teachers believe they learn to teach. The challenges and complexities of museum teaching are revealed and analyzed in order to identify effective approaches to training and development. While agreeing that all aspects of teacher understanding are important, the author concludes that pedagogical content knowledge, or the blending of content and pedagogy, is the area on which museums must focus in order to fulfill the potential of museum teachers and teaching. (Contains 21 notes.)