While Grosse and Voght (1991) set out a well-considered overview of LSP and identified areas in need of development, they limited their observations on the topic of assessment to a short section devoted to what they called the proficiency movement. While it is true that they really did not have a lot to report on at the time they wrote their review, and that this current review highlights much interesting work done in the area in the intervening years, there remains a considerable emphasis on practice rather than on theory, with published papers attempting to identify solutions to given assessment problems, rather than attempting to build cohesive assessment theories. The primary focus of this contribution is on the latter aspect of language assessment. The article first offers a historical overview of the area over the past twenty years, which moves from a brief discussion of the issues highlighted by Grosse and Voght to the theoretical issues that have emerged, and finishing with a critical review of research on issues around assessment in three specific domains (immigration and citizenship, or work and the professions). The article then highlights current needs and priorities, focusing on issues of test usage and introducing the concept of test localization before presenting the core of the argument: a theory of LSP assessment validation. It concludes with a preliminary attempt to exemplify how a theory-driven research agenda can inform future research, and ultimately, practice in the area of LSP assessment over the coming decades.IN JUNE 1999, JOHN WALSH, IN AN IRISH Independent news article, reported that the Irish education minister had decided to end the practice of requiring all teachers in the Republic of Ireland to have successfully passed a test in the Irish language before having their post made permanent. The test used was the Ceard Teastas Gaeilge (literally the "Irish language craft certificate"), which tested a person's ability to perform his or her job through the medium of the Irish language. The certificate had, at one time, been required of all state employees, including university lecturers, lawyers, and civil servants, with different versions for different professions, including for different school subjects in the case of teachers.When I qualified as a secondary school teacher in the summer of 1977, I sat such a test. This marked my first encounter with a test of language for specific purposes.The view of specific purpose language use that influenced the developers of the Ceard Teastas Gaeilge was quite sophisticated for that time, with items related to lexis (i.e., in the version I sat, these items tested the lexis of engineering) and to actual classroom practice, in which the candidate was asked to indicate how a specific skill might be taught to a group of learners. The awareness that specific purpose assessments should be precise (Douglas, 2001) and explicitly related to a particular domain of language use was clearly embedded in the test. Today, assessment instruments have been develop...