This study examines measures of formative assessment practice using data from a study of the implementation and effects of adding curriculum embedded measures to a hands-on science program for upper elementary school students. The authors present a unifying conception for measuring critical elements of formative assessment practice, illustrate common measures for doing so, and investigate the relationships among and between scores on these measures. Findings raise important issues with regard to both the challenge of obtaining valid measures of teachers' assessment practice and the uneven quality nature of current teacher practice. (Contains 11 tables and 2 figures.)