To determine whether students are engaged in reflective practice it is necessary to have some means of identifying reflective thought and a measure of the depth of reflective thinking. Several measures of reflectivity have been proposed but there appears to be no widely accepted and clearly formulated procedure for determining levels of reflective thinking from students' written reflective journals. In this study we propose a scheme for estimating the quality of reflective thinking in students' writing in reflective journals, using categories based on Mezirow's work on reflective thinking. In an initial test of the scheme, reasonable levels of agreement were obtained from eight judges. Disagreements over coding resulted from differing interpretations of the significance of what students had written rather than from a lack of precision in the guidelines for coding categories. A second test, using students' reflective papers, showed acceptable levels of reliability between four assessors. The method is recommended for both assessing students and evaluating courses in programs which aim to develop reflective thinking.