Shadowing is a theoretically and empirically well-examined method to develop L2 learners’ listening comprehension (input effect); enhance their subvocal rehearsal mechanism in the phonological working memory for learning new words, formula, and constructions (practice effect); simulate some stages of speech production (output effect); and develop metacognitive monitoring and control by their executive working memory (monitoring effect). In Japan and some other Asian countries, shadowing is a well-recognized, popular method of learning English and Japanese as L2, and this book offers the chance for anyone new to this method to benefit. Through the research contained within this book, readers will be armed with detailed and useful accounts of the four effects above (i.e. input, practice, output, and monitoring effects) from a theoretical and empirical viewpoint.