Anecdotal evidence from teachers who teach in bilingual or second language settings indicates that there is a potential for loss of subject matter. This loss is particularly troubling within the context of science learning. This article reviews several projects aimed at developing an understanding of the implications of bilingual instruction in student outcomes and for student success. Twenty students were asked to read four different texts in Spanish: one narrative, and three expository texts which covered science concepts. Children were asked to read and recall the texts in the language in which they felt most comfortable. They were then interviewed in groups about reading in science. In addition, the children's English language California Achievement Test (CAT) scores in reading, vocabulary, and mathematics were collated. All reading scores in Spanish, the second language, significantly intercorrelated (ranging from .83 to a low of .78) and significant relationships existed between the CAT vocabulary measures (in English) and two of the reading scores and between the CAT reading scores in English and three of the Spanish reading passages. It is concluded that the children in the study indicate they are potentially proficient users and doers of science, that this using and doing is visible through literacy-related activities and materials, and is potentially masked by performance assessment. Contains 10 references. (LZ)