A project to field test instruments and procedures for measuring English language proficiency, to be used in a large-scale national household survey, is reported. The major purposes of the field test were to measure the validity of census-type questions for determining language proficiency, using several different bilingual ethnic groups, and to evaluate proposed data collection procedures for the larger study. The report begins with an overview of the project. Chapter 2 explains the design of the original field test, revisions made to it, and site selections. The third chapter describes sampling activities: securing school district cooperation, obtaining lists of students, and selection of sample individuals. Samples were drawn from Miami (Florida), El Paso (Texas), San Francisco (California), and Ganado and Window Rock (Arizona). Data collection activities are outlined in chapter 4, and analysis activities are described and results are presented in chapter 5. Appended materials include the bilingual study census questionnaire and compilations of additional results of discriminate analysis. (MSE)