It is my pleasure to introduce this thematic issue dedicated to the lexicography of Japanese as a second or foreign language, the first thematic issue in Acta Linguistica Asiatica since its inception.Japanese has an outstandingly long and rich lexicographical tradition, but there have been relatively few dictionaries of Japanese targeted at learners of Japanese as a foreign or second language until the end of the twentieth century. With the growth of Japanese language teaching and learning around the world, the rapid development of very large scale linguistic resources and language processing technologies for Japanese, a new generation of aggregated, collectively developed or crowd-sourced resources evolving in the context of the social web, a shift from static paper to constantly developing electronic resources, the spread of internet access on hand-held devices, and new approaches to the use of language reference resources stemming from these developments, dictionaries and other reference resources for learners, teachers and users of Japanese as a foreign/second language are being developed and used in new ways in different user communities. However, information about such developments often does not reach researchers, lexicographers, dictionary users and language teachers in other user communities or research spheres. This special issues wishes to contribute to the spread of such information by presenting some recent developments in this growing field.Having received a very lively response to our call for papers, not all papers selected for publishing could fit into this issue, and part of them will be included in the December issue of ALA, which is also going to be dedicated to Japanese lexicography.The first round of papers included in this issue presents a varied cross-section of current JFL lexicographical work and research. All papers in this issue point out the relative scarcity of appropriate reference works for learners of Japanese as a foreign language, especially when compared to lexicographical resources for Japanese native speakers, and each of the endeavours presented here confronts this lack with its own original approach. Reflecting the paradigm shift in Japanese language research, where corpus research is again playing a central role, most papers presented here take advantage of the bounty of newly available corpora and web data, most prominent among which is the Balanced Corpus of Contemporary Written Japanese developed by the National Institute for Japanese Language and Linguistics in Tokyo, and which is used by Mogi, Pardeshi et al. and Sunakawa et al. in their lexicographical research and projects, while Blin taps data for his research from the web, another increasingly important linguistic resource.The first two papers offer two perspectives on existing Japanese dictionaries. Tom Gally in his paper Kokugo Dictionaries as Tools for Learners: Problems and Potential points out the drawbacks of currently available Japanese dictionaries from the perspective of learners of Japanese as a foreign language, but at the same time offers a very detailed and convincing explanation of the merits of monolingual Japanese dictionaries for native speakers (kokugo dictionaries), such as their comprehensiveness, detailedness and quantity of contextual information, when compared to bilingual dictionaries, which make them a potentially useful resource even for an audience they are not targeting - foreign language learners. His detailed explanation of possible uses and potential hurdles and pitfalls learners may encounter in using them, is not only accurate and informative, but also of immediate practical value for language teachers and lexicographers.Toshinobu Mogi, in his paper Towards the Lexicographic Description of the Grammatical Behaviour of Japanese Loanwords: A Case Study, investigates the lexicographic description of loanwords in Japanese reference works and notes how information offered by currently available dictionaries, especially regarding the grammatical aspects of loanword use, is not sufficient for learners of Japanese as a foreign language. After pointing our the deficiencies of current dictionary descriptions and noting how dictionaries sense divisions do not reflect the frequency of different senses in actual use, as reflected in a large-scale representative general corpus of Japanese, he uses a fascinatingly detailed analysis of the behaviour of a Japanese loanword verb to describe a corpus-based method of lexical description, based on the correspondence between usage forms and senses, which could be used for the compilation of Japanese learners' dictionaries meant for the reception and production of Japanese.The second part of this special issue is composed of four reports on particular aspects of ongoing lexicographical work targeted at learners of Japanese as a foreign language.Prashant Pardeshi, Shingo Imai, Kazuyuki Kiryu, Sangmok Lee, Shiro Akasegawa and Yasunari Imamura in their paper Compilation of Japanese Basic Verb Usage Handbook for JFL Learners: A Project Report, after pointing out - as other authors in this issue - the lack of a detailed and pedagogically sound lexicographical description of Japanese basic vocabulary for foreign learners, propose a corpus-based on-line system which incorporates insights from cognitive grammar, contrastive studies and second language acquisition research to solve this problem. They present their current implementation of such a system, which includes audio-visual material and translations into Chinese, Korean and Marathi. The system also uses natural language processing techniques to support lexicographers who need to process daunting amounts of corpus data in order to produce detailed lexical descriptions based on actual use.The next article by Marcella Maria Mariotti and Alessandro Mantelli, ITADICT Project and Japanese Language Learning, focus on the learner's perspective. They present a collaborative project in which Italian learners of Japanese compiled an on-line Japanese-Italian dictionary using a purposely developed on-line dictionary editing system, under the supervision of a small group of teachers. One practical and obvious outcome of the project is a Japanese-Italian freely accessible lexical database, but the authors also highlight the pedagogical value of such an approach, which stimulates students' motivation for learning, hones their ICT skills, makes them more aware of the structure and usability of existing lexicographic and language learning resources, and helps them learn to cooperate on a shared task and exchange peer support.The third project report by Raoul Blin, Automatic Addition of Genre Information in a Japanese Dictionary, focuses on the labelling of lexical genre, an aspect of word usage which is not satisfactorily presented in current Japanese dictionaries, despite its importance for foreign language learners when using dictionaries for production tasks. The article describes a procedure for automatic labelling of genre by means of a statistical analysis of internet-derived genre-specific corpora. The automatisation of the process simplifies its later reiteration, thus making it possible to observe lexical genre development over time.The final paper in this issue is a report on The Construction of a Database to Support the Compilation of Japanese Learners’ Dictionaries, by Yuriko Sunakawa, Jae-ho Lee and Mari Takahara. Motivated by the lack of Japanese bilingual learners' dictionaries for speakers of most languages in the world, the authors engaged in the development of a database of detailed corpus-based descriptions of the vocabulary needed by learners of Japanese from beginning to advanced level. By freely offering online the basic data needed for bilingual dictionary compilation, they are building the basis from which editors in under-resourced language areas will be able to compile richer and more up-to-date contents even with limited human and financial resources. This project is certainly going to greatly contribute to the solution of existing problems in Japanese learners' lexicography.