Language for specific purposes (LSP) has a long history in the language testing literature. An outgrowth of the communicative language movement of the 1970s, LSP testing arose out of the practical need to assess individuals’ abilities to perform specific tasks in academic and professional settings. This historical review traces the evolution of LSP testing in the language testing literature, focusing specifically on theory and research in two key areas: (a) authenticity and (b) the interaction between language knowledge and background knowledge. The review then turns to how Douglas (2000), in the most comprehensive treatment of LSP testing to date, incorporates insights from these two lines of work into his conceptualization. Throughout the review, tensions and debates emerging from the literature are discussed. The final section addresses the uncertain future of LSP in the language testing landscape.