Assessing generally refers to the process of gathering information about a person relative to specific competencies and other attributes, in formal or informal learning contexts. This should lead to valid and reliable inferences about competency levels, which in turn may be used for diagnostic and/or predictive purposes. Too often, classroom and other high-stakes assessments are used for purposes of grading, promotion, and placement, but not to enhance learning. In this chapter, we focus on formative assessment which posits that assessment should (a) encourage and support, not undermine, the learning process for learners and teachers; (b) provide formative information whenever possible (i.e., give useful feedback during the learning process instead of a single judgment at the end); and (c) be responsive to what is known about how people learn, generally and developmentally. This type of assessment has as its primary goal improvement of learning, which is critical to support the kinds of learning outcomes and processes necessary for students to succeed in the twenty-first century. It is referred to as 'formative assessment,” or assessment for learning, in contrast to 'summative assessment” (or assessment of learning). This chapter overviews the role of formative assessment in education generally, and also touches on stealth assessment specifically—an ­evidence-based approach to weaving assessments directly into learning environments (Shute, Computer games and instruction. Charlotte, NC: Information Age Publishers, 2011).