ENCommunication is one of the basic and most important forms of human activity. Convention and its application is the most important means in achieving an understanding. By convention we mean unvvritten and uncodified expectations, stemming from experience shared by members of a given community. It is convention that raises expectations, such as that people should behave or dress within certain norms, or that they should respond in a predictable way in a given situation. A conception of other people (for example representatives of other nations, religions or races) established in awareness of members of a community is referred to as a stereotype. Every society makes use of many stereotypes which influence the process of communication betvveen individuals, groups of people, and whole nations. In the Polish society we can differentiate a distinct stereotype of a Jew, German, Russian, Gypsy, etc. The process of establishing a stereotype is long and complex, and unlikely to change. This paper is an attempt to reveal a stereotype of a Pole in Lithuania and a Lithuanian in Poland, and to identify the main factors which have influenced its historical and contemporary aspects. The theses of this paper were juxtaposed with views expressed by politicians, representatives of political sciences, and authorities in international relations. Data obtained from a questionnaire investigating the way Poles and Lithuanians perceive other nations35 completes the picture of Polish-Lithuanian relations.