This handbook describes the nature, uses, and limitations of the Modern Language Association of America (MLA) language proficiency tests for teachers and advanced students. The proficiency tests are examined in seven areas of language teaching competence: listening comprehension, speaking, reading, writing, applied linguistics, civilization and culture, and professional preparation. Several articles examine the validity of the tests and discuss related research. The final section focuses on the potential and limitation of the tests. Appendixes contain information concerning the MLA teacher qualifications, test scores and NDEA Institute ratings, MLA Proficiency and MLA Cooperative Tests, Foreign Service Institute rating scale, comparative test scores of Institute and native speakers, and NDEA Institute norms for the MLA Proficiency Tests, 1961-67. (RL)