In this paper, the verbal interaction strategies and explanation behaviors of three fifth-grade teachers teaching science units are used to illustrate relationships among curriculum materials, teacher talk, and student learning. Experimental studies with these and other teachers indicate that, if teachers become more sensitive to their students' thinking and need for conceptual change and modify their verbal instruction accordingly, student understanding and learning of science can be improved. Textbooks and other curriculum materials can either help or hinder this process. (Author)