A Hong Kong program to train secondary school teachers in the use of English as the medium of classroom instruction is reported and discussed. The program provides assistance to teachers accustomed to using mixed code in the classroom and who must use English consistently, and helps English teachers understand how they can support teachers of other subjects in an English-medium instruction (EMI) school. The report first outlines the qualities needed by an EMI instructor, including language proficiency, skills and strategies for teaching through a second language, and attitude and background knowledge that contribute to a commitment to change. It then describes briefly the design and content of the program that helps teachers improve in those areas. Lessons learned in the first year about the adequacy and acceptability of the course to teachers, and consequent course changes, are then examined. It was found that the most important areas needing strengthening are those relating directly to the special role of an immersion teacher in teaching both content and second language. Finally, other forms of support needed and Hong Kong efforts to provide these are noted. (Contains five references.) (MSE)