Since 1997, the "biliterate and trilingual" policy has been adopted by the Hong Kong government, and is now guiding the curriculum design in Hong Kong primary schools. This language policy aims to ensure that Hong Kong students become biliterate (written English and Chinese) and trilingual (spoken English, Cantonese and Putonghua). However, Hong Kong primary schools currently do not have an agreed method for the implementation of trilingual education. As a preliminary step in the investigation of methods of the implementation of trilingual education in Hong Kong primary schools, we carried out a detailed case study of the trilingual education model adopted in a primary school. Views of key stakeholders (the principal, teachers, students and parents), on how successful the model is, were collected, and a number of lessons taught using English, Cantonese or Putonghua as the medium of instruction were recorded and analysed. On the basis of the research findings, a possible model for implementing trilingual education in Hong Kong primary schools has been suggested. (Contains 4 tables and 1 figure.)