The published literature on writing to learn in science was reviewed in order to develop a conceptual framework for readers of this special issue and an agenda for future research. Professional journals, books, ERIC documents, and doctoral dissertations were consulted in this review process. Research on writing to learn has been hindered because studies have not always been well designed or clearly reported, and few have been conducted in authentic classroom environments. Furthermore, the links between writing to learn and conceptual change, and writing to learn and critical thinking have not received sufficient attention. Carefully designed studies, both qualitative and quantitative, are still required to provide data from a variety of perspectives. Because the reported studies at the college level outnumber those at other levels, research is still required to generalize the findings across a variety of science classrooms and to elucidate principles for guiding effective teacher use of writing-to-learn strategies.