This paper seeks to unpack some dimensions of formative assessment not yet fully articulated in the existing literature. It introduces the term, pre-emptive formative assessment to denote teacher actions which attempt to clarify student understandings before misconceptions have resulted in ineffective learning outcomes and/or loss of marks in assignments or examinations. It is suggested that this dimension is common in practice but its principles and practice have not yet been conceptualized. The rationale for pre-emptive formative assessment stems from key issues in the provision of useful feedback, namely timeliness and the opportunity for students to act. An example of pre-emptive formative assessment is described and issues in its implementation discussed. Limitations of pre-emptive formative assessment are examined. The paper concludes by arguing that pre-emptive formative assessment is worthy of wider attention, and outlines some directions of further exploration and ongoing data collection. (Contains 1 figure.)