Over the past few years, language testing research has been focusing on performance tests, rather than traditional paper-and-pencil tests. This change of focus is closely related to a world-wide trend in education, namely, the progressive introduction of criterion-referenced assessment and the harmonizing of this with norm-referenced assessment. In the light of these current trends, the present study attempts to develop descriptors which could be used to describe the oral proficiency of language learners, on the basis of the theoretical framework shown in Council of Europe (2004). It is expected that these descriptors will be of considerable assistance to Japanese teachers of English and will enable them to make more reliable judgments on their students' performance.