ENEver since the union of 1386 between Poland and Lithuania, the nobility of the Grand Duchy of Lithuania strove to enhance the position of their polity within the Polish-Lithuanian Commonwealth. In their instructions for envoys to the sejm, or parliament, to the king or other dignitaries, the Lithuanian sejmiki, that is, provincial assemblies of the nobility, while acting mostly to uphold the union, at the same time emphasized the need to observe the rights of the Grand Duchy. It is difficult to establish whether they regarded Lithuania as one of the two entities that made up the Commonwealth, or rather as one of its three principal provinces (Greater Poland and Lesser Poland being the other two). The majority of the issues raised in the instructions belong to the various demands of the nobility, who had mostly their own interests at heart, or are related to the developments that benefited high-ranking office holders. Keywords: The Grand Duchy of Lithuania; the Polish-Lithuanian union; the nobility; sejm; sejmik. [From the publication]