This paper presents the development of Ajdukiewicz's conception of analytic sentences. Starting from his pre-war radical conventionalism, the presentation proceeds to Ajdukiewicz's moderate aposteriorism and, finally, to radical aposteriorism. Various accounts of analyticity by Ajdukiewicz are mentioned and briefly commented on. At the end of the paper, Ajdukiewicz's influence on Polish philosophy in regard to the issue of analyticity is pointed out.