Book excerpt: When learners of a new language draw on their native language (or on any other that they may know), this earlier acquired linguistic knowledge may influence their success. Such cross-linguistic influence, also known as language transfer, has long raised questions about what linguists can predict about success in the new language and about what processes are involved in using prior knowledge. This book lucidly brings together many insights on transfer: e.g. on the relation between translation and transfer, the relation between comprehension and production, and the problem of how complete any predictions of difficulty may ever be. The discussions also explore implications for future research and for classroom practice. The book will thus serve as a reliable guide for teachers, researchers, translators, interpreters, and students curious about language contact.