Abstract
This paper is primarily a methodological consideration, which critically reviews the literature on using protocol analysis to understand cognitive processes that students engage in while writing language tests. For the purpose of synthesizing the applicability and significance of protocol analysis in validating language tests, the author first discusses the potential of the concepts including validity, language test validation, and protocol analysis. Terminological classifications of different approaches of test validation are elaborated. The author then critically examines the state of evidence by interpreting studies that employed protocol analysis in language tests. This paper is intended to stimulate discussion on the merits and inadequacies of protocol analysis in different ESL/EFL tests, especially when the tests are designed for test-takers with culturally different backgrounds. Possible future research trends are suggested.