While English has become the lingua franca of global science, it has been well-established that especially in the social sciences and humanities (SSH), communication of original research results in multiple languages is an ongoing practice (Kulczycki et al., 2020). But are the natural sciences, engineering, medicine and agriculture as research fields entirely dominated by English language communication? Standard publication and citation databases, notably Web of Science and Scopus, predominantly index peer-reviewed articles published in international English language journals. This means that research published in languages other than English remains invisible. In addition, these databases ignore science communication, which is specifically targeted to professional and general audiences outside academia. In this study we rely on more comprehensive data sources developed in Poland and Finland by integrating publication data from local Current Research Information Systems (CRIS) of universities (Sile et al., 2018). Our aim is to investigate and compare the multilingual publishing patterns across the OECD major field classifications (OECD 2007), i.e. Natural Sciences, Engineering and Technology, Medical and Health Sciences, Agricultural Sciences, Social sciences, and Humanities. The main research questions are: 1. How many languages individual researchers at Polish universities use in publishing peer-reviewed outputs, and what is the share of English, national language and the other languages, across the OECD main fields? 2. How many languages are used, and what is the share of English, national languages and the other languages, in the peer-reviewed publication output of Finnish and Polish universities across the OECD main fields? 3. How large share of the non-peer-reviewed publication output (targeted mainly to professional and general audiences) of the Finnish universities is in English, national languages and the other languages across the OECD main fields? We created two datasets to investigate these questions: Polish dataset consists of bibliographical records of 67,413 researchers affiliated with Polish higher-education institutions or research institutes, and their 1,031,141 peer-reviewed outputs published in 2013-2016, from the Polish Scholarly Bibliography, which is part of the Polish current research information system POL-on (Korytkowski & Kulczycki, 2019). Finnish dataset consists of 74,987 peer-reviewed and non-peer-reviewed publications (publication year 2019-20), the metadata of which is recorded in the national VIRTA Publication Information Service. The VIRTA data is validated and reported by the 13 Finnish universities annually to the Ministry of Education and Culture (Pölönen & Auranen, 2022). References: Korytkowski, P. & Kulczycki, E. (2019). Dominant language of researchers across fields, RESSH Conference 2019. https://ressh2019.webs.upv.es/wp-content/uploads/2019/10/ressh_2019_paper_21.pdf Kulczycki, E., Guns, R., Pölönen... (2020). Multilingual Publishing in the Social Sciences and Humanities: A Seven‐Country European Study. Journal of the Association for Information Science and Technology, 71, 1371-1385. https://doi.org/10.1002/asi.24336 Pölönen, J. & Auranen, O. (2022). Research performance and scholarly communication profile of competitive research funding: the case of Academy of Finland. Scientometrics (in print). Sile, L., Pölönen, J., Sivertsen... (2018). Comprehensiveness of national bibliographic databases for social sciences and humanities: findings from a European survey. Research Evaluation, 27(4), 310–322. https://doi.org/10.1093/reseval/rvy016