A study of biliteracy focuses on discourse as the unit of analysis needed to understand the task facing bilingual students. It investigated the way in which 22 high school students representing six different language groups in a bilingual basic skills course struggled with scientific language in an experiment on the community's drinking water. Most students were not literate and had had no previous science experience. During the investigation, students began to appropriate the intentional possibilities of language in order to construct scientific meanings and resolve a dilemma posed by the evidence at hand. It is concluded that while in traditional book-based bilingual education, students are expected to assimilate decontextualized language, this active learning approach causes students to construct both language and content knowledge by confronting authentic dilemmas. A 34-item bibliography is included. (MSE) (Adjunct ERIC Clearinghouse on Literacy Education)