Book excerpt: This book examines the use of tasks in second language instruction in a variety of international contexts, and addresses the need for a better understanding of how tasks are used in teaching and program-level decision-making. The chapters consider the key issues, examples, benefits and challenges that teachers, program designers and researchers face in using tasks in a diverse range of contexts around the world, and aim to understand practitioners’ concerns with the relationship between tasks and performance. They provide examples of how tasks are used with learners of different ages and different proficiency levels, in both face-to-face and online contexts. In documenting these uses of tasks, the authors of the various chapters illuminate cultural, educational and institutional factors that can make the effective use of tasks more or less difficult in their particular context.