One major impact of globalisation on education is denoted by the growing trend to use English, the global language, as a medium of instruction (MOI) in emerging polities that are trying to enhance their English-speaking capacities. This article emphasises developing an understanding of MOI from a language policy and planning as well as an educational perspective. It explores the policy and practice of MOI in 10 polities in Asia including Bangladesh, Hong Kong, India, Indonesia, Japan, Malaysia, the Maldives, Nepal, Timor-Leste and Vietnam, using a broad-based framework that aims to explicate the context, motivation, goals, actors, implementation process and outcomes of MOI. The article points out the dominance of English as MOI which is used in eight of the polity studies included in our analysis. We conclude that while the Asian region as a whole reflects the globalisation of English as medium of instruction policies, individual polities may have specific motivations and goals and that they may develop specific strategies to protect their own interests and identities. More crucially, at the macro-policy level, there seems to be a simplistic understanding of MOI as a cheap solution to complex language problems for achieving overly ambitious politico-economic goals and that this leads to less than ideal MOI implementation illustrated by teachers' and students' struggles as policy actors at the micro level. (Contains 1 table and 2 notes.)