This paper reports a study of the effects of a collaborative inquiry approach to science on language minority students' (middle and high school) learning. This approach emphasizes involving the students, most of whom have had very little schooling, in "doing science" in ways that scientists practice. This study addresses the question: To what extent do students appropriate collaborative scientific inquiry? The authors focus the analysis on changes in students' conceptual knowledge and use of hypotheses, experiments, and explanations to organize their reasoning in the context of two think-aloud problems. The findings indicate that at the beginning of the school year the students' reasoning was non-analytic and bound to personal experience. By contrast, at the end of the school year they reasoned in terms of a larger explanatory system; used hypotheses to organize and give directions to their reasoning; and demonstrated an awareness of the function of experimentation in producing evidence to evaluate hypotheses. (Author/PR)