This paper explores limits and possibilities for students' book bags as data sources in educational research. A discussion of the feasibility of book bags as data sources is followed by a brief description of an ethnographic research project focused on literacy and schooling in families of General Education Diploma (GED) students. The larger study explored literacy practices that were present in homes where both children and parents were engaged in literacy learning. Specifically, I explore two related research questions: (1) What items do children and adults carry in their book bags?; and (2) How well do the contents of book bags represent children's and adults' home and school experiences? Examination of both children's and adults' book bags revealed insights into the types of literacy activities children and adults were engaged in at school. The role book bags played in crossing borders between home and school and how well the contents of book bags reflected children's home and school lives were explored. The paper concludes by considering insights gleaned from examining book bags and makes recommendations for the future use of book bags as data sources. (Contains 5 tables.)