Although the importance of language in science learning has been widely recognized by researchers, there is limited research on how science teachers perceive the roles that language plays in science classrooms. As part of an intervention design project that aimed to enhance teachers' capacity to address the language demands of science, interview data (N = 9) were collected to understand teachers' perceptions and experiences with a wide range of issues related to language use in science classrooms. Adopting an interpretive approach to qualitative data, the analysis revealed that the teachers perceive a wide range of student difficulties related to language use in science classrooms, especially to the use of specialized terms and writing. Although the teachers are keenly aware of how language can be a barrier to learning science, they are less certain as to what students need to know about the language of science in order to master it. The findings suggested professional support that highlights the distinctive language demands of science and how these demands differ from other subject areas could be useful to these elementary school teachers.