The presence of many languages in our society and our classrooms has implications for conducting research, both in terms of the validity of the research and the broader social responsibilities of the mathematics education research community. This paper argues that in some ways mathematics education research causes or reproduces the educational and social disadvantage of researchers, teachers, and students of less favored languages. Two conference papers reporting research into multilingual issues in mathematics teaching and learning are examined as a way of considering such issues in more detail. Brief suggestions are offered for a way forward. (Contains 34 references.) (Author/KHR)