Fettes (2004) asserts that "politico-strategies" of languages are no longer viable frameworks for "national and community policy". Rather, he proposes the development of "geostrategies of interlingualism", i.e. linguistic strategies which promote international communication equitably and efficiently, whilst respecting and ensuring language maintenance and pluralism. He asserts that the future development of interlingual communication will depend upon chosen communicative device(s). To date research has focused on "the advocates, developers and practitioners of each approach" (p. 38) independently rather than on the influence of these instruments in combination on communities of speakers at micro and meso-levels. Supranational organisations serve as important sites of investigation for language planners interested in studying multi-functional/lingual communication. One such organisation is the "International Maritime Organisation", established in 1958 to facilitate cooperation among governments in matters of international shipping. Currently 165 countries (and three associates) constitute its membership. There are six official and three working languages. This paper discusses the nature of interlingualism at IMO, investigating whether the instruments in place ensure equitable and efficient communication. Multilingual practices are guaranteed at the highest levels of political representation but at lower levels English functions as the main tool of communication. Comparisons are made with other supranational organisations. (Contains 7 figures and 3 tables.)