This article deals with the history of magnetron oscilladons research in the former Czechoslovakia in the 1920s -1950s, primarily with the work of Czech physicist August Zacek (1886-1961), his students and colleagues at Charles University in Prague, and with the work of Czech physicist Josef Sahanek (1896-1942) from Masaryk University in Brno. The question about magnetron research during WWII and in the first post-war decade is open up.