Ernesto Macaro, Professor of Applied Linguistics at the University of Oxford, gives a talk for the Department of Education public seminar series. The exponential growth of English Medium Instruction (EMI) both in Higher and Secondary Education globally has resulted in a similar growth of empirical research on the subject. Of necessity this research to date has been exploratory, single institution-oriented and lacking a clear research agenda that a more established community of practice might have ensured. In this talk I will present some findings from a systematic review of EMI that we have carried out in the EMI Oxford Centre as well as some of our own research. I will conclude with recommendations of what research still needs to be done in order to ensure that decision makers in education are fully informed of its potential dangers as well as its possible benefits. Ernesto Macaro is Professor of Applied Linguistics at the University of Oxford where he is Director of the Centre for Research and Development in English Medium Instruction (EMI Oxford) in the Department of Education