This study was undertaken to better understand what happens when teachers implement a reform curriculum designed specifically to communicate mathematics content and pedagogy to teachers. More specifically, the study focuses on what aspects of the curriculum materials teachers consider as they decide what they will enact in the classroom. Information was gathered to determine the extent to which teachers were understanding the main mathematical content of their first unit on number, the kinds of thinking that students were intended to develop, and how useful the supporting materials embedded in the curriculum were in helping them enact the curriculum. The findings in this study about what teachers learn from this supporting information should be of interest to researchers, curriculum developers, and professional development providers as they consider ways to support teachers' implementation of reform curricula. (Author)