The correspondence between Kazimierz Twardowski (1866–1938) and Alexius Meinong (1853–1920) contains interesting material on three matters, namely: 1) their research work, 2) the creation and functioning of psychological laboratories in Graz and Lvov, 3) the atmosphere in philosophical centers in German-speaking areas (mainly in Austria-Hungary). A part of Twardowski's letters, stored in the archives of Vienna University, has been published.¹ A large collection of Meinong's letters quoted in this paper are preserved in the Kazimierz Twardowski Archive.² Meinong's letters, all of them typed, have Twardowski's notes with the dates of his replies. It enables us, despite the fact that many of Twardowski's letters are missing, to trace the records and frequency of correspondence between the two scientists.