The present text is the first attempt in historiography to evaluate the scientific output of Józef Andrzej Gierowski from the perspective of research into the parliamentarism of the Polish-‑Lithuanian Commonwealth. Out of the 482 publications written by him between 1946 and 2006, 20 were selected which were directly or significantly devoted to parliamentarism. The influence of Gierowski's on the study of parliamentarism was not limited to publications, but included the shaping of successive generations of historians of political history and political systems (including parliamentarism), through the promotion of master's and doctoral theses and numerous reviews in promotion proceedings and publishing procedures. A key role in promoting the results of his own research, as well as his profound reflections on the function-ing of parliamentarism, its role in the former Republic, and its significance on against the backdropground of the processes of change of the political systems of Europe at that time, is occupied by the extremely widely read syntheses of Polish history by Gierowski. He should therefore be regarded as one of the key figures in the field of research into Polish‑Lithuanian parliamentarism.