Given the growing importance of education abroad in language curricula and the potential that it holds for investigating psycholinguistic processes and the interactions that individual, linguistic, and cultural variables have on multiple skill areas, this timely volume will be of interest to scholars, language teachers, and those who design and run study abroad (SA) programs. Reporting on longitudinal (2.5 years), multivariate data from the Study Abroad and Language Acquisition (SALA) Project conducted at two Spanish universities (in Barcelona and Palma de Mallorca), this volume examines learners’ progress in oral, written, and intercultural domains as a result of two learning contexts—SA and formal instruction (FI). Among the many strengths of this large-scale, quantitative volume are its methodological soundness (e.g., utilizing a controlled, repeated-measures design and a large sample size); the inclusion of productive and receptive, oral and written data for phonology, lexicon, syntax, discourse, and intercultural awareness that correlate with data for individual differences, length of stay, retention, and proficiency at onset; the in-depth examination of European learners in two learning contexts (SA and FI); and the inclusion of baseline data from native speakers. This work helps to lead us in a new direction by going beyond simply comparing at home and SA learners and focusing instead on granularity within the SA group to better interpret variability in learners’ performance. Sanz contextualizes the project within SLA research in Chapter 1. The common methodology is explained in Chapter 2, followed by the details of the study program itself in Chapter 3. Chapters 4 to 12 report on a variety of gains in the FI and SA contexts for 3-month and 6-month sojourns abroad in English-speaking cities as well as retention 15 months later. In Chapter 4 the author finds that learners’ oral accuracy significantly improved while abroad, especially for those with lower accuracy scores at the onset of SA, and the results held over time. Similarly, Chapter 5 reports improvement of learners’ oral fluency while abroad, but gains were not affected by onset level; amount of contact with native speakers abroad also seems to influence fluency. Chapters 6 and 7 deal with phonological development and reveal that 3 months was insufficient time to observe gains in pronunciation accuracy, and 6 months abroad yielded only minor changes. On a phonological discrimination task, the SA context failed to yield significant improvements, but in the FI context learners showed significant gains. Listening comprehension abilities, examined in Chapter 8, increased while abroad (but not after FI), especially for lower level learners. Academic writing is the focus of Chapter 9, and, like the previous chapter, results show significant gains (in written fluency, accuracy, and complexity) after SA but not FI. Chapter 10 reveals improvement in lexicogrammatical abilities for learners in both contexts. However, there is variation when it comes to the effects of motivation and other psychosocial attributes (Chapter 11). Finally, Chapter 12 examines intercultural awareness and finds that learners were significantly more open to the host culture after SA, but the effect was not retained over time. As a valuable bookend to Sanz’s introduction in Chapter 1, DeKeyser takes the discussion of the variables to the next level in Chapter 13 and makes suggestions for future directions. The findings of this volume take into account what prior studies have contributed and lay further, solid groundwork for future research. Learning context matters but not in the same way for everyone or every area of language. Because one of the key findings across the chapters has to do with length of stay, future studies should also examine with greater subtlety how shorter term programs, which are the growing trend in the United States, affect learners’ development. By designing SA programs that sequence practice in the various skill areas in accordance with learners’ levels and by taking into account individual differences, we can better prepare learners for a world that increasingly demands multilingual and multicultural skills.