The 42th meeting of the ICES Working Group on Introductions and Transfers of Marine Organisms (WGITMO) was held in Olbia, Italy, 16–18 March 2016, with Anna Occhipinti-Ambrogi as host and Henn Ojaveer as chairperson. Representatives from 19 countries participated in the meeting. Attendants were from Belgium, Canada, Dennark, Estonia, Finland, France, Germany, Ireland, Israel, Italy, Lithuania, Norway, Poland, Portugal, Russia, Spain, Sweden, United Kingdom and United States. Sweden contributed by cor-respondence. The objectives of the meeting were to update information and discuss several aspects related to the introductions and transfers of non-indigenous aquatic species. Data and information management were two of the discussion topics of the meeting, with special focus on the better exploitation of the ‘Information system on aquatic non-indigenous and cryptogenic species’ (AquaNIS). The WGITMO also dedicated time for addressing the MSFD D2 issues: indicator on new non-indigenous species introduced by human activities, and opportunities and problems related to cross-regional comparison of non-indigenous species indicators. Preparation of the manuscript of the alert report on sea squirt Didemnum vexillum, which is to be published in ICES CRR series, was discussed and the steps to be taken to finalise the report were agreed. As usual, adequate time was devoted to discuss national reports, to exchange of information on the management of NIS and to review ongoing and planned research activities. The approach taken during the meeting facilitated presentations and discussions on the issues of relevance related to the Terms of References as well as on a few generic and strategically-important issues of general relevance to bioinvasions. The meeting began with a full-day joint meeting with the Working Group on Ballast and Other Ship Vectors (WGBOSV), which provided an opportunity to discuss and address issues of common interest, such as shipping and biofouling as introduction vectors. The proposed ICES demonstration advice on ‘Risk management of non-indigenous species associated with shipping in the Arctic’ was discussed, and edits were suggested for both the orientation of the demonstration advice as well as for the exact questions to be asked. Both working groups agreed that the practice of conducting back-to-back meetings with one joint day is useful and will continue in 2017. All Terms of References to be addressed for 2016 were discussed. For some Terms of Ref-erence, more detailed presentations were given, and a short overview of the information and subsequent discussion is provided herein at the end of each section. This report is structured so that each Term of Reference is dealt with in sequential order. The main body of the report contains summaries of the presentations and discussions with the more detailed documents being contained in the Annexes. WGITMO progressed each of the Terms of Reference by either completing the task or clearly identifying and agreeing on the inter-sessional activities required to still finalise the work in 2016. From 2017, WGITMO will be shifted to multi-annual management.