This study examined urban elementary teachers' knowledge and practices in teaching science while supporting English language development of English language learning (ELL) students. As part of a larger 5-year research project in the United States, the study involved 38 third-grade teachers who participated in the first-year implementation of a professional development intervention that consisted of curriculum units and teacher workshops. The study examined four areas - teacher knowledge of science content, teaching science for understanding, teaching science for inquiry, and teacher support for English language development - through a questionnaire, classroom observations, and post-observation interviews. Results indicate that teachers' knowledge and practices were generally within the bounds supported by the intervention; however, such knowledge and practices fell short of the goal of reform-oriented practices. The results provide insights for our ongoing intervention and other similar efforts and contribute to the emerging knowledge base on science and English language and literacy with ELL students. (Contains 9 tables and 3 figures.)