Open AccessFairness has been the priority in educational assessments during the past few decades. Differential item functioning (DIF) becomes an important statistical procedure in the investigation of assessment fairness. For any given large-scale assessment, DIF evaluation is suggested as a standard procedure by American Educational Research Association, American Psychological Association, and National Council on Measurement in Education. This procedure often affords opportunities to check for group differences in test performance and investigate whether or not these differences indicate bias. However, current DIF research has received several criticisms. Revisiting DIF, this paper critically reviews current DIF research and proposes new directions for DIF research in the investigation of assessment fairness.