In this study, we examined how in-service middle-level mathematics teachers used statistics in their own classroom research. Using an embedded single-case design, we analyzed a purposefully selected sample of nine teachers' classroom research papers, identifying several themes within each phase of the statistical problem solving process to summarize how teachers 1) planned studies and collected data, 2) analyzed data, and 3) interpreted results. The results illustrate the varying ways in which teachers used statistics to make data-based decisions about their classrooms, revealing teachers' early development in their statistical thinking and suggesting that teachers' required knowledge of statistics is multi-faceted, requiring both a pedagogical component and statistical knowledge for the teaching profession. Such findings have important implications for how we, as teacher educators, can best meet teachers' professional needs.