This book offers new insights into the language gains of adult learners enrolled in an English-medium instruction (EMI) degree programme. It provides longitudinal empirical evidence of the phonological gains of the learners; discusses which individual factors contribute to the changes in the learners’ pronunciation and investigates whether and to what extent increased exposure to the target language in EMI classrooms leads to incidental learning of second language pronunciation. Furthermore, it expands on the discussions surrounding the Critical Period Hypothesis, the native-speaker norm, foreign language accent and the role of English as a Lingua Franca. The comparative and longitudinal design of the research study fills a significant gap in the literature and the book offers considerable original and important research-informed insights into the fields of EMI, bilingual education and second language acquisition. As such, it is a valuable resource and must-read book for researchers, practitioners and policymakers in these areas.