Reflective thinking is often stated as a learning outcome of baccalaureate nursing education, and as a characteristic of a competent professional; however, no consistent method exists to assess the extent to which students engage in reflective thinking. To address this need, Kember and Leung developed and tested a self-report questionnaire based on Mezirow's conceptualisation of levels of reflective thinking. The purpose of this study was to test the psychometric properties of the Reflection Questionnaire, developed by Kember and Leung. A convenience sample ("n"?=?538) of third-year baccalaureate nursing students from four collaborative nursing programmes in Ontario was used. Ethical approval was secured from 10 sites. Second-order confirmatory factor analyses (CFA) were used to test the factor structure of the Reflection Questionnaire. This research was part of a larger study on reflective thinking and is a first step in validating a four-level measure of reflective thinking, in educational environments, with baccalaureate nursing students. The results of the second-order CFA provide support for the construct validity of reflective thinking. Results of this study contribute to the evidence supporting the reliability and validity of the questionnaire. Nurse educators can use this information when implementing the questionnaire, and learning the extent to which students are engaging in the reflective thinking process. (Contains 9 tables and 7 figures.)