This report is one of five submitted as products of a "Study Designed to Assist Planning of Research on Significant Instructional Features in Bilingual Education Programs." The reports are intended to assist the National Institute of Education (NIE) in its plans for a major new research study in bilingual education. The present volume is a discussion of working definitions of terms for use in the features study. The terms discussed are "bilingual education,""consequences for children,""instructional features,""significant," and "model." Alternative definitions and the implications of each for design are presented. The definitions selected by NIE are intended to guide the research to be conducted. (Author/JB)