In 1969, the Philadelphia Museum of Art posthumously presented Marcel Duchamp’s last monumental installation Étant donnés, which he had been working on in secrecy for at least 20 years while ‘officially’ occupied with playing chess. Whereas the earlier The Large Glass in its enigmatic structure had inspired Duchamp’s contemporaries to multiple interpretive approaches and was recognised by criticism as arguably one of the most formative art works of the twentieth century, the reactions towards Étant donnés ranged from awkward silence to blunt rejection. The installation so impertinently contrasted with all of the artist’s prior expressions that initially by intuition it was taken as nothing but a bold provocation. This paper analyses the influence of Marcel Duchamp’s intensive chess praxis on his late installation Étant donnés. With the study of chess, it asks why it was necessary to take the risk of being misunderstood and what was at stake in the conception of Duchamp’s last masterpiece; it asks in what way the rules, strategies, tactics and conventions of the chess game influenced the artistic sensibility and thinking of Marcel Duchamp in conceptualising Étant donnés. ‘Through’ these, it observes the inner organisation of the site specific installation, especially in regard to its relation with the viewer and Duchamp’s own positioning within the art world. It does so always with one eye on The Large Glass, Étant donnés’ half-identical twin and Marcel Duchamp’s ‘other’ masterpiece.