Considerable literature is devoted to teachers' assessment use to support teaching and learning. The study examined the factor structure of a measure of teachers' assessment use along the assessments "of", "for", and "as" learning purpose dimensions. The study also examined the factor structure of teachers' perceived instructional usefulness of these dimensions. Together, the measure provides a pulse on classroom assessment practice. The validation effort 1) presents the Classroom Teacher Assessment Use and Usefulness Survey, CTAUUS, for use in research on teachers' assessment practice, and 2) provides empirical grounding for the distinction among the purpose-related dimensions. Exploratory factor analyses revealed two identical factors for use and usefulness: AoL, with five items on the use of standardized assessments; and a combined AfL and AaL factor with nine items that we had anticipated as two separate factors. The study contributes to developing understanding of the conceptualization and measurement of AfL and AaL constructs.