Science notebooks can be a formative assessment tool for both teachers and students to determine: (1) prior knowledge and existing science ideas; (2) how conceptual understanding is being built; (3) procedural understanding; (4) mastery of curriculum goals; and (5) the ability to apply/transfer ideas to new context (Volkmann & Abell, 2003). Using science notebooks with preservice teachers accomplishes two goals: (1) It introduces preservice teachers to a beneficial assessment tool; and (2) It provides information on preservice teachers' science conceptual understanding and process skill knowledge. Writing about science in their notebooks is an important step in the development of preservice teachers' science literacy (content knowledge, inquiry skills and disposition toward using critical thinking/science reasoning in decision-making). This article reports a study which focused on the science notebook as a formative assessment tool in a science methods course and the resultant views held by preservice teachers on the value of this assessment tool for their future practice. (Contains 2 figures.)