The oral proficiency interview, a one-to-one conversational interview structured to elicit the best performance the student can sustain, is based on a scale and test developed 30 years ago by the Foreign Service Institute. Interest in it has increased substantially in recent years, and further research and development of the measure for use in a variety of situations have been undertaken. It was found that, as a result of a training course given to test administrators, some teachers altered the curriculum, classroom activities, materials, and pace of instruction to help students cross the major thresholds between one proficiency level and the next. Several curriculum development projects have grown out of the American Council on the Teaching of Foreign Languages/Educational Testing Service (ACTFL/ETS) oral proficiency projects, including one aimed at restructuring a secondary-level French program based on the ACTFL proficiency guidelines and one creating a fourth-year college conversation course designed to move students from the intermediate to the advanced level. The ACTFL/ETS guidelines and tests based on them can serve as an organizing principle for curriculum development and provide a basis for the elaboration of end-of-course goals. They have been found to be more effective than other instructional strategies in helping students emerge from language study with a usable level of language skill. (MSE)