This article deals with an innovative adult education program during the Popular Front. While the lectures broadcast by the Centre Confédéral d’Education Ouvrière (CGT’s working-class education center) are often cited, they are rarely studied. Created in 1933 as a way to democratize knowledge, the CCEO had the opportunity in 1937 to gain access to the mass media and to enlarge its audience. This article illuminates how during three years it broadcast “La voix de la CGT”, the trade-union confederation gained a better sense of the special demands posed by a broadcast program. During this period, it tried to both fulfill its educational mission and struggle against the temptations of propaganda.