High-stakes testing is one of the most controversial issues in American education. Advocates contend that these tests encourage students to work harder, provide teachers with a stronger understanding of students' strengths and weaknesses, and allow educators to target failing schools for extra help. Critics claim that they narrow and distort the curriculum, hold students and teachers with inequitable resources to the same standards, and solidify class and ethnic disparities. This Information Capsule reviews research conducted on the unintended consequences of high-stakes testing programs, such as narrowing of the curriculum, higher levels of student test anxiety, and increased pressure on teachers. In addition, high-stakes tests have been found to have a disproportionately negative impact on low-performing, low-income, and minority students. Although the majority of unintended consequences are negative, researchers have found that high-stakes tests have some positive effects on education, including increased teacher professional development, better alignment of instruction with state content standards, more effective remediation programs for low-achieving students, and increased use of data to inform instruction. The research is mixed on the impact of high-stakes testing on dropout rates, students' levels of academic achievement and motivation, and on the consequences of publishing test scores. This report also includes a brief review of studies that have examined the full costs of high-stakes testing.