Timor-Leste offers a rich case study of the array of discursive influences on medium-of-instruction (MOI) policy in multilingual, post-colonial developing contexts. MOI policy in this young nation is a site of tension between struggles to define national identity in the shadow of colonial language ideologies and the globalised discourses of powerful international development aid partners. Guided by the notion of opening up ideological and implementational space for non-dominant languages in education, this article reviews the evolution of MOI policy in East Timorese primary education over the decade since independence. Paying particular attention to recent proposals for mother tongue-based multilingual education, the review highlights the ideological nature of the relationship between language planning and the MOI. The East Timorese case shows how MOI policy emerges from historical and socio-political experiences and is shaped by complex interactions between external and internal forces. (Contains 1 table and 18 notes.)