The aim of this volume is to highlight the benefits and potential of using learner corpora for the testing and assessment of L2 proficiency in both speaking and writing, reflecting the growing importance of learner corpora in applied linguistics and second language acquisition research. Identifying several desiderata for future research and practice, the volume presents a selection of original studies, covering a variety of different languages. It features studies that present very thoroughly compiled new corpus resources which are tailor-made and ready for analysis in LTA, new tools for the automatic assessment of proficiency levels, and new methods of (self-)assessment with the help of learner corpora. Other studies suggest innovative research methodologies of how proficiency can be operationalized through learner corpus data. The volume is of particular interest to researchers in (applied) corpus linguistics, learner corpus research, language testing and assessment, as well as for materials developers and language teachers.