Going beyond measuring accuracy of teachers' judgments of students? achievements, this paper focuses on how prospective elementary teachers proceed in one-on-one diagnostic mathematics interviews. As part of the project diagnose:pro, prospective elementary teachers (PTs) conduct diagnostic interviews with children in grade one and reflect on diagnostic strategies afterwards. Findings of the study lead to a model of strategic elements in diagnostic proceeding and suggest types of diagnostic strategies. It is also discussed how awareness of diagnostic strategies can be developed to foster sensitive every-day qualitative diagnostic attitudes in PTs. [For the complete proceedings, see ED597799.]