The Common European Framework of Reference for Languages (CEFR) and its Companion Volume have established themselves as an indispensable reference point for all aspects of second and foreign language education. This book discusses the impact of the CEFR on curricula, teaching/learning and assessment in a wide range of educational contexts, identifies challenges posed by the Companion Volume and sheds light on areas that require further research and development. Particular attention is paid to three features of the two documents: their action-oriented approach, their focus on plurilingualism, and the potential of their scales and descriptors to support the alignment of curricula, teaching/learning and assessment. The book suggests a way forward for future engagement with the CEFR, taking account of new developments in applied linguistics and related disciplines.