Concepts of second language proficiency and how proficiency may be assessed have changed considerably over the last 20 years. New notions of validity with respect to the interpretation and uses of test scores have begun to shape discussions about test validity and quality assurance in college world language departments, in government, and in business, obliging us to revisit established methods of proficiency assessment. This article first discusses the evolution of the term proficiency, particularly in its use within the U.S. government starting in the 1950s and by ACTFL starting in the 1980s. It will then examine how test theory, especially the notion of validity, has changed in the last 30 years in the field of educational measurement, and it will argue that Evidence-Centered Design (ECD) (Mislevy, Steinberg, & Almond, [Mislevy, R. J., 2002]), a model that grew out of task-based language assessment (TBLA), may help us better conceptualize language proficiency assessment. After a discussion of what is currently known about proficiency levels of German students in U.S. colleges, some promising developments in proficiency assessment, which have the potential to considerably increase student proficiency levels, will be identified.