The English General Scholastic Ability Test (GSAT), a nationwide high-stakes college entrance exam in Taiwan, has commonly served as a placement test for streaming college freshmen into EFL classes. There has, however, been scant research reported on the feasibility of using an admission test for EFL placement. This study aims to investigate the accuracy and validity of placement decisions being made using the English GSAT scores, with a focus on its relations with the General English Proficiency Test (GEPT) and students’ subsequent performance in class. Quantitative data, including the English GSAT scores, the GEPT High-Intermediate Listening and Reading scores, and the English final course grades, were collected and statistically analyzed from four EFL classes with a total of 100 students at a university in Taiwan. The English GSAT was found to function well to place students into distinctively lower or higher level of EFL classes but did not discriminate well for the borderline cohort. A three-level placement using the English GSAT appeared to be a better differentiation between each proficiency cluster. High achievers in the English GSAT appeared to perform better on the GEPT listening and reading tests than did low achievers. Yet, apart from the GEPT reading test, the English GSAT yielded weak predictive power of student course attainment, which seemingly varied across classes, hinging on course designs and grading policies. Implications drawn from the results of the investigation were further discussed.