The Education Department of Hong Kong issued the Medium of Instruction Guidance for Secondary Schools in October 1997. The policy stipulates that the use of Chinese as the medium of instruction in all but English language and literature subjects in secondary schools will be enforced with effect from September 1998. This signals a change in language policy in post-1997 Hong Kong, from bilingual to monolingual education. Traditionally English medium instruction has been more popular than Chinese medium instruction in Hong Kong secondary schools. Despite the Hong Kong government's recent efforts to promote Chinese medium education, the number of Chinese-medium schools was small before the handover. This is a documentary study investigating changes in Hong Kong government's medium of instruction policy amid political, economic and sociolinguistic changes in the last three decades. The study also explores some possible impact of the Chinese medium instruction policy proposed in the wake of change of sovereignty on English language learning. I will critique this new policy and make recommendations pertaining to the direction of Hong Kong's language education. The theoretical underpinning of the study is bilingualism and bilingual education. The model I propose will provide new insights for language teachers, language planners and policy makers.[Copyright of International Journal of Bilingual Education and Bilingualism is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/13670059908667684]