The General English Proficiency Test (GEPT) is a 5-level, criterion-referenced English as a Foreign Language (EFL) testing system implemented in Taiwan to assess the general English proficiency of EFL learners. In 1999, with the aim of encouraging the general study of English and to result in beneficial washback effects on the teaching and learning of English, the Ministry of Education lent its support to the Language Training and Testing Center in the development of the GEPT. Throughout a decade of efforts, the GEPT has won popular recognition in Taiwan. To date, more than 4.3 million Taiwanese have taken the test. This article first documents the evolution of the GEPT from the perspectives of test development and validation. The article then provides an overview of how GEPT scores are used in both educational and professional domains and discusses several key issues and problems that have emerged due to the new context introduced by the GEPT. Finally, the article outlines how the GEPT will address the challenges it faces in the years to come. (Contains 3 tables.)