The study examined US elementary teachers' knowledge and practices in four key domains of science instruction with English language learning (ELL) students. The four domains included: (1) teachers' knowledge of science content, (2) teaching practices to promote scientific understanding, (3) teaching practices to promote scientific inquiry, and (4) teaching practices to support English language development during science instruction. The study was part of a larger five-year research and development intervention aimed at promoting science and literacy achievement of ELL students in urban elementary schools. It involved 32 third grade, 21 fourth grade, and 17 fifth grade teachers participating in the first-year implementation of the intervention. Based on teachers' questionnaire responses and classroom observation ratings, results indicated that (1) teachers' knowledge and practices were within the bounds of acceptability but short of reform-oriented practices and (2) grade-level differences existed, especially between Grades 3 and 5. (Contains 5 tables.)