This paper tries to give answers for successful receptive multilingualism (RM) but also for its failure. It is mainly based on the results of two projects, one on inter-dialectal communication in the Baltic area during the era of the Hanseatic League and the other analyses inter-Scandinavian communication today. The main purpose of this survey is to outline the essential preconditions for successful RM, from a linguistic, social and environmental perspective. The historical project about communication in the Baltic focuses on long-term language contact based on common mutual trading interests whilst the contemporary project highlights the cultural factors (among others Pan-Scandinavism) as a common basis for using one's own mother tongue in transnational communication. Moreover, other relevant issues belonging to successful RM are touched upon, such as diglossia (i.e. the functional distribution of different languages/varieties in various settings), oral face-to-face communication, the absence of written norms and the non-existence of standardised forms, which result not only in a greater flexibility in communication but also support openness for divergent varieties. Disfavouring factors for RM are, however, taken into consideration as well, such as nationalism and the suppression of minorities (and thus indirectly multilingualism), the enforcement of strict linguistic norms by the society and finally the use of a lingua franca such as Latin in the Middle Ages or English today.