The Significant Bilingual Instructional Features (SBIF) descriptive study identified, described, and verified important features of bilingual education for instuction of limited English proficient students. Part I involved the study of 58 classrooms and 232 students, grade K-12, at six diverse sites representing a variety of ethnolinguistic (Mexican, Puerto Rican, Cuban, Cantonese, and Navajo) and multilinguistic groups. The classrooms were nominated for their success as settings for bilingual instruction. A variety of qualitative and quantitative procedures were used to collect data on instructional organization, time allocation, teacher characteristics, classroom language use, students' academic learning time, and student participation styles. The investigation indicated that the nominated classrooms were characterized by (1) congruence of instructional intent, (2) use of active teaching behaviors, (3) use of the students' native language and English for instruction, (4) integration of English language development with basic skills development, and (5) use of information from the students' home culture. (MSE)