Content and language integrated learning (CLIL) is characterized by using students’ additional language (L2) as the medium of instruction of non-language content subjects. In recent decades, this type of program has been gaining worldwide popularity, especially in English-as-a-foreign-language (EFL) contexts, because of the assumption that it can facilitate L2 learning. However, this assumption may not be realized in many classrooms in EFL contexts, where both teachers and students are often not well-prepared to cope with the heavy linguistic demands to learn content and language simultaneously. Owing to a combination of sociopolitical and socioeconomic forces, Hong Kong has a rather long history of practicing some form of CLIL in secondary schools, in the form of English-medium instruction (EMI) education. Following some recent changes in the government’s medium of instruction policies, there are different models and practices of EMI in Hong Kong schools to accommodate students with different English proficiency levels and also the expectations of different stakeholders. This chapter will illustrate these different models and practices and discuss their implications and challenges for English language learning, content learning, and teacher education. Copyright © 2019 Springer Nature Switzerland AG.