The purpose of this investigation was to explore elementary teachers' beliefs about data and data use. Archived data from 2 research projects were used to address the following research questions: What are kindergarten and fifth-grade literacy teachers' beliefs about data and data use? What functions do the beliefs serve in teachers' actual use of data? Using a multicase study approach, 2 research teams carried out qualitative data analysis. Findings revealed that kindergarten and fifth-grade teachers held similar "macro" beliefs, and these beliefs were shaped and contextualized in response to their settings. The study's implications suggest that teachers' beliefs about data are influential in what teachers actually view as data and in the ways they put data to use to address students' learning needs.