Multilingualism is a broad term that alludes to the use of several languages (not necessarily proficiently) via the mutual interaction of languages in the mind of the user or with others. Thus, it does not only target language use, but how prior linguistic and cultural experience of such users contributes to determining their communicative competence. Interest in multilingualism is growing fast in research, education, and policy. This volume addresses current research in multilingualism from such diverse education contexts as Spain, Costa Rica, Mexico or Japan in order to provide an insight into the variety and diversity of research problems in the field. Acknowledging that research questions are to still further face the challenges posed by different contexts of practice in primary, secondary and tertiary levels, this collection is divided into ten chapters that approach the selected issues from different empirical perspectives, bringing together research in relevant contextual levels and emphases such as language, content and skills acquisition, learning and teaching effectiveness, policy supervision and motivational factors.