Until recently, the assumption of the language-teaching literature has been that new languages are best taught and learned monolingually, without the use of the students' own language(s). In recent years, however, this monolingual assumption has been increasingly questioned, and a re-evaluation of teaching that relates the language being taught to the students' own language has begun. This article surveys the developing English language literature on the role of students' own language(s) in the language classroom. After clarifying key terms, the paper charts the continuing widespread use of students' own languages in classrooms around the world and the contemporary academic and societal trends which have led to a revival of support for this. It then explores key arguments which underpin this revival, and reviews a range of empirical studies which examine the extent and functions of own-language use within language classrooms. Next, the article examines the support for own-language use that a range of theoretical frameworks provide, including psycholinguistic and cognitive approaches, general learning theory and sociocultural approaches. Having explored the notion of "optimal" in-class own-language use, the article then reviews research into teachers' and students' attitudes towards own-language use. It concludes by examining how a bilingual approach to language teaching and learning might be implemented in practice.