This study focuses on the characteristics of discourse between Latino immigrant children and their teacher during science instruction. Peer interaction was analyzed to identify the use and importance of the native language (L1) for the development of content knowledge during group collaboration. In addition, the interaction between teacher and children was analyzed to determine the importance of the adult's use of the L1 in providing instructional support to make science and literacy meaningful for linguistically and culturally diverse students. Classroom observations over the course of 1 year focused on how a Spanish-English bilingual teacher approached the demands of science inquiry in an urban fourth-grade classroom in northern California. The analysis centers on a discourse analysis of the students' conversations while they participated in and completed a science activity. In their conversations, children employed different discourse strategies to accomplish their communicative goals during the science activities. Whereas Spanish was the main language of instruction during the science activity, children also used English and code-switches to challenge each other, reinforce major science concepts, and develop literacy skills. Discourse strategies that can promote academic achievement among English language learners through the use of their native language are discussed. (Contains 5 endnotes.)