This report describes the role of analogies in science instruction and presents research on a model for teaching with analogies. This model is being developed from research studies of textbooks and exemplary teachers; it provides guidelines for the strategic use of analogies during science instruction to explain fundamentally important concepts in ways that are meaningful to students. The model shows how exemplary teachers and textbook authors construct effective analogies to help students build upon new knowledge learned from textbooks by activating, transferring, and applying relevant existing knowledge. Contains 10 references and 4 figures illustrating analogies used in science instruction. (Author)