In this article, the authors propose cultural-historical activity theory as a framework for understanding the opportunities that arise for students and teachers from the presence of researchers in the classroom. They analyze three vignettes from their research in elementary mathematics classrooms for the purpose of illustrating a cultural-historical activity theoretic explanation of the interaction. Finally, the authors suggest that the “impact” of research can be increased at least locally when participants capitalize on the opportunities that arise for teaching and learning when researchers are present.