Terence Odlin reconsiders a question that many language teachers and educational researchers have addressed: How much influence can a learner's native language have in making the acquisition of a new language easy or difficult? Odlin analyzes and interprets research showing many ways in which similarities and differences between languages can influence the acquisition of grammar, vocabulary, and pronunciation. In addition, he provides a detailed look at work on other areas important for the study of transfer, including discourse, individual variation, and sociolinguistic factors. Language teachers, applied linguists, and educational researchers will find this volume extremely valuable to their work.