Growing mobility of important parts of the world's population has led to a massive increase in multilingualism in post-modern societies and a lasting change from homoglossic to polyglossic communities with important "deterritorialised” linguistic minorities, mostly plurilingual to a variable degree. Ideologies and practices of communication in old and new multilingual contexts vary largely. The "solutions” for overcoming potential problems go from using a lingua franca (often English), inventing pidgin like emergent varieties, choosing the language of one of the interlocutors known (partially) by the others (namely in the case of immigrants), insisting on receptive competences (everybody uses his or her own language, e. g. in officially multilingual institutions), to various forms of mixed speech and, of course, to interpretation and translation processes. Drawing on extensive field work in bilingual institutions and multilingual companies in Europe, particularly in Switzerland, we propose to discuss various ways of mobilizing multilingual repertoires in situations of cross-linguistic and intercultural communication. The analyzed data will mainly consist of dyadic and polyadic oral interactions. It will also include written texts and signs that are part of the linguistic landscape. Our work is grounded in the assumption that multilingualism is no longer considered a marginal phenomenon, only of interest to specialists, but instead a characteristic of the majority of human being