Based on an innovative corpus-based approach, this book offers a comprehensive survey of the phonological and phonetic properties of L2 speech in English and German. The first part of the book critically examines current theoretical models and research methodologies in the field of second language acquisition of phonology and describes the advances that have been made in corpus linguistics over the past few years -- in particular, the development of phonological learner corpora. It furthermore presents the first learner corpus of L2 English and L2 German that is fully aligned and has extensive phonological annotations: the LeaP corpus. The second part of the book describes the results of the quantitative and qualitative corpus analyses in the following areas of non-native speech: fluency, final consonant cluster realisation, vowel reduction and speech rhythm, intonation and general foreign accent. In addition, the influence of many non-linguistic factors, including instruction and a stay abroad, on the phonological properties of non-native speech is explored.