Research is reviewed on second language learning and implications for student assessment and placement of limited English proficient (LEP) students in special education are addressed. To support her contention that the most effective mode of instruction for an LEP child requiring special education should be within the framework of the child's own language and culture, the author cites research on the following topics: similarities and differences in the acquisition of first and second languages, transfer of concept development in the first language to the second language, differences in problems of second language acquisition versus learning disorders (language disorders present more complexity because they stem from a variety of sources), and reasons for greater benefits from special education in the child's native language (primarily for affective reasons). Needs for appropriate assessment instruments and instructional materials are noted. (CL)