This qualitative, sociolinguistic research study examines how bilingual Latino/a students use their linguistic resources in the classroom and laboratory during science instruction. This study was conducted in a school in the southwestern United States serving an economically depressed, predominantly Latino population. The object of study was a fifth grade science class entirely comprised of language minority students transitioning out of bilingual education. Therefore, English was the means of instruction in science, supported by informal peer-to-peer Spanish-language communication. This study is grounded in a social constructivist paradigm. From this standpoint, learning science is a social process where social, cultural, and linguistic factors are all considered crucial to the process of acquiring scientific knowledge. The study was descriptive in nature, examining specific linguistic behaviors with the purpose of identifying and analyzing the linguistic functions of students' utterances while participating in science learning. The results suggest that students purposefully adapt their use of linguistic resources in order to facilitate their participation in science leaning. What is underscored in this study is the importance of explicitly acknowledging, supporting, and incorporating bilingual students' linguistic resources both in Spanish and English into the science classroom in order to optimize students' participation and facilitate their understanding.