Immersion, a relatively new approach to bilingual education, orginated in Canada. It uses the target language as a medium of instruction in order to achieve "additive bilingualism"-- a high level of second language proficiency added to normal development in the L1. The wide range of languages and purposes now served by immersion worldwide is illustrated by case studies of thirteen programs presented and discussed in this book. The introductory chapter defines immersion education theory and practice and shows how this approach differs from other forms of bilingual education.