This article presents a case study incorporating English teachers' perspectives into the development of a large-scale international English assessment, the recently developed "TOEFL Junior"® Comprehensive test. It discusses how stakeholder feedback gathered during test development supports the validity argument for score interpretation and the use of a newly developed test. When the pilot version of the test was administered, focus-group interviews were conducted to gather teacher perspectives on the test. Teachers of English as a foreign language in Korea from different types of institutions--public schools, private mainstream schools, and private after-school English enrichment programs--were invited to participate. This article discusses how the interviews were conducted and summarizes the teachers' major comments about the test. Then, it discusses how the teachers' recommendations and suggestions were reflected in the final test design decisions. During the decision-making process, the teachers' comments were examined in light of various statistical results, such as interitem correlations and generalizability analyses. The article concludes with a broader discussion of how teachers' perspectives, which have not often been incorporated into the development of large-scale international assessments, can make an important difference in designing a test and, consequently, enhance the validity of the test.