In contemporary Estonian education there are currently two types of CLIL programs – one which is based on a foreign language, such as the English language, and the other being based on a national language, i.e. the Estonian language. Although there is a longstanding tradition of CLIL in Estonia, the study of CLIL programs is in its infancy. At present, the research has been focusing only on the implementation of Estonian-based CLIL syllabi while no research has been conducted about the foreign language based CLIL programs in Estonia. Thus the current work attempts to study the application of English-based CLIL in Estonian secondary schools. The focus of the book is primarily on analyzing the application of CLIL from Estonian teachers' perspective and presenting a profile of Estonian CLIL teacher. The target groups for the book would be professionals who are interested in studying the daily practices of CLIL teachers, or anyone who would like to gain knowledge about content-and-language-integrated learning.