The recent No Child Left Behind legislation has defined a vital role for large-scale assessment in determining whether students are learning. Given this increased role of standardized testing as a means of accountability, the purpose of this article is to consider how individual differences in motivational and psychological processes may contribute to performance on high-stakes math assessments. The authors consider individual differences in processes that prior research has found to be important to achievement: achievement goals, value, self-concept, self-efficacy, test anxiety, and cognitive processes. The authors present excerpts from interviews with eighth-grade test takers to illustrate these different achievement-related motivational beliefs, affect, and cognitive processing. Implications for future research studying the situational pressures involved in high-stakes assessments are discussed. (Contains 2 notes.)