OEI #90-91: Sickle of Syntax & Hammer of Tautology offers the first English language overview of the history of concrete and visual poetry production in socialist Yugoslavia between 1968 and 1983. By focusing on mass-produced examples of concrete poetry, this publication presents these poetic experiments as organically linked to social movements, critical theories, and youth cultural revolutions. In his extensive introduction, Sezgin Boynik, the guest editor of this special issue of OEI, discusses concrete and visual poetry in socialist Yugoslavia as an uneven and combined development, and emphasizes its confrontational and organizational aspects. By means of interviews, translations, reproductions, and theoretical and historical statements, OEI #90-91 offers a picture of a very lively scene of concrete and visual poetry in Yugoslavia, which unfortunately is not as recognized internationally as it would deserve. Hoping that OEI #90-91 could contribute to this task in a substantial way, we present episodes from the early years of OHO formation and its complex theories of words and things; an interview with Rastko Mocnik on programmed art and political formalism; militant polemics of Goran Babic; Signalist contradictions; subjective structural devices of Judita Šalgo; zaum experiments of Vojislav Despotov; detective meta-texts of Slavoj Žižek; poetic self-management studies of Vujica Rešin Tucic; a feminist historicisation of Ažin school for experimental poetry; democratisation of visual poetry by Westeast; selections from special issues of the journals Pitanja, Problemi, Ulaznica, Dometi, Delo, Koraci, Vidik, Pegaz, and many other materials translated here for the first time and presented in one publication.