The subject of the article is the language of Wiech (Stefan Wiechecki's) writings and its relation to Warsaw slang. The author analyses 200 before-the-war writings and a similar number of post-war ones to find slang features and the so-called 'wiechisms', i.e. surprising word connections based on really existent slang elements. The analysis aims at providing an answer to the question if the quantity of Warsaw slang features differs in the two periods and what is the frequency of using the slang in the texts. Warsaw slang is linguistically essential for Wiech's writings. Specifying phonetic, morphological and syntactic features as well as lexical analysis resulted in figures and allowed to define the degree of slang condensation in both groups of writings. The analysis attempts to answer how the explorer of Warsaw slang transformed into its creator after 1945