The influential position of Jaroslav Bidlo (1868-1937) among Czech(oslovak) historians was based not only on his full profesorhip at the Faculty of Arts of Charles University, but also on his membership in several societies. He actively used acquired possibilities to promote historical Slavonic studies or to help his younger colleagues with their first steps in their academic careers.
The paper focuses on Bidlo's membership in two most important Czech(oslovak) scientific societies: the Royal Bohemian Society of Sciences (Královská česká společnost nauk, KČSN) and the Czech Academy of Sciences and Arts (Česká akademie věd a umění, ČAVU).