A study explored children's notions of what stories and reports are, how they can be organized, and when to use them, as revealed in the stories and reports they wrote or recalled and in their responses to questions about each. Sixty-seven high achieving children in grades three, six, and nine read and wrote similar kinds of stories and reports. This permitted comparison of ways in which they organized their knowledge across genre and domain. Findings indicated the following: (1) children have strongly differentiated notions of stories and reports and structure them in different ways from early in their lives, (2) they use these structures in the pieces they read and retell as well as in the ones they write, (3) both stories and reports grow in complexity along a variety of measures, and (4) both stories and reports show increased student control of genre-related organizational structures as children develop. (Author)