Abstract: The ACTFL Proficiency Guidelines (ACTFL, 1982; 1986; Breiner-Sanders et al, 2000) and the Oral Proficiency Interview (OPI) derived from them have stimulated abundant and sustained professional engagement by foreign language teachers at all levels and in all languages, as well as intense and equally sustained criticism by specialists in foreign language testing. This paper presents (1) a brief history of the genesis of the Guidelines, (2) a summary of the criticisms leveled against them, and (3) an analysis of the reasons for the continued significance of the Guidelines in curricular and testing initiatives during the last two decades at both state and national levels.