The Yugoslav Radical Union (Jugoslovanska radikalna zajdenica) was founded for the whole of Yugoslavia in the second half of 1935, soon to be followed by its youth organization that was supposed to promote the principle of »state and national unity« in the spheres of politics, social services, education and sports. In Slovenia, then a part of the Drava Banovina, the Youth of the Yugoslav Radical Union (YYRU) (Mladina Jugoslovanske radikalne zajednice) was linked directly to the Slovenian part of the Yugoslav Radical Union (the former Slovenian Peoples Party - Slovenska ljudska stranka). In May 1939, the YYRU had 293 locals with approximately 11,000 members. The author establishes that YYRU was the political branch of the Unions of Boys' Sections (Zveza fantovskih odsekov) in the Drava Banovina, and that it paved the way for the Catholic sociological school - the Christian solidarity that eventually grew into the s.c. Christian social action in mid-Thirties.