The development and field testing of a proficiency test in English as a Second Language for non-native speakers teaching on Guam is reported. The resulting instrument measures four language skills (listening, reading, writing, and speaking). The listening measure uses natural language that might be heard by a classroom teacher. The reading measure is based on authentic materials for Guam educators, including department of education publications and professional journals. The writing measure consists of a holistically scored essay on an educationally relevant topic and task, and a multiple-choice portion requiring the prospective teacher to identify errors in three simulated student essays. The speaking measure is an oral proficiency interview. The report describes the needs assessment, test construction, field testing and revision, and the setting of appropriate passing scores on each test section. Recommendations for the implementation of an operational testing program are made, taking into account the particular circumstances of the Guam Department of Education. Appended materials include the needs analysis report, item specifications and samples, instructions, scoring guides, and other information related to test development and administration. (MSE)