After China resumed the sovereignty of Hong Kong, the Curriculum Development Council encouraged schools to experiment with Putonghua as a medium of instruction (PMI) to teach the Chinese language. A review of the literature indicates that there have been problems in implementing the switch to the new medium of instruction (MOI). The aim of this exploratory case study is to investigate in more detail the problems that teachers and administrators of a secondary school face in implementing the new policy. Based on interviews, classroom observation, and documentary analysis, it is shown that conflicts and tensions have arisen from the incongruent beliefs of teachers and administrators regarding the rationale and impact of the PMI policy. Moreover, inadequate knowledge of Putonghua among teachers and students, a shortage of appropriate teaching resources, and the absence of helpful support from the government create further barriers to effective teaching and learning in the new programme. This paper argues that it is problematic for schools to translate any MOI policy into action if policy-makers fail to address the challenges that teachers and administrators encounter in switching to a new MOI.[Copyright of Language, Culture and Curriculum is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/07908318.2011.626863]
