In the archive of the Centre d’Estudis Històrics Internacionals del Pavelló de la República, among the hundreds of boxes with items of Jordi Arquer’s collection (Barcelona, 1907-Perpignan, 1981) gathered throughout his life, we must highlight more than thirty boxes that contained his mail from 1939 to 1976, although he died in 1981. Thousands of letters and hundreds of correspondents are saved. The themes are always the same: the war, the exile, the workers’ movement, socialism and communism, and the future of Catalonia. Now, we present a brief selection of a hundred (exactly 104, including the four of George Orwell) to release the interest of this person and his archive collection. Arquer was a bibliophile, a researcher of the events and the people of the war and communism. Everything turns his documents into a key base for the communism issues, at home and abroad. We must consider the selection presented as provisional, as a sample. The thousands of letters gathered ask for a long and patient archive work, which, when done, will give as result hundreds of impassioned pages, if wanted with subjective opinions about Catalonia and the social left. Professor Josep Termes i Ardèvol has made the labour of selection, the notes and the introduction.