The Test of German as a Foreign Language (TestDaF) plays a critical role as a standardized test of German language proficiency. Developed and administered by the Society for Academic Study Preparation and Test Development (g.a.s.t.), TestDaF was launched in 2001 and has experienced persistent annual growth, with more than 44,000 test takers in 2016 (a 16% increase over the previous year; g.a.s.t., 2017). Of note, and in keeping with the motto of "Study successfully in German," TestDaF is one of a suite of products and services offered by g.a.s.t. and intended to facilitate access to German university studies, including the following: an Internet-based platform for individualized language learning (Deutsch-Uni Online or DUO); an online assessment for placing students into foreign language courses (onSET); and a university aptitude assessment, the Test for Academic Studies (TestAS). On its website, g.a.s.t. provides ample information regarding all of these products for different audiences, including test takers, test centers, universities, and teachers. This current review focuses on TestDaF. The primary purpose of TestDaF is to provide a determination of the adequacy of a candidate's German language proficiency.