After the decisions of the XV Congress of the AUCP(b) in December 1927, the activities of the left opposition (i.e., supporters of the bloc of L. D. Trotsky and G. E. Zinoviev) was outlawed, and its program was declared a Menshevik bias. Most of the opponents of the Stalin-Bukharin course was forced to capitulate, i.e. to announce the rejection of their own views in order to preserve their place in the party. However, hundreds of oppositionists in the largest cities of the USSR refused to act on principles and continued to work underground. One of the cen-ters of the communist underground was Leningrad, where communist groups of various orientations operated a few years earlier: Zinovievites, Trotskyists, Decists, the workers' opposition and others. Since 1923, students have traditionally been responsive to opposition views, which continued to play prominent roles in the struggle of 1928–1929. The objective of the research is to reconstruct the activities of the Leningrad opposition in the underground, to assess its number, to identify the role of students. The main materials for the preparation of the article will be documents from the collections of the Central State Archive of Historical and Political Documents of St. Petersburg (CSAHPD St. Petersburg) and the Russian State Archive of Socio-Political History (RSASPH), as well as a digitized part of the archive of L. D. Trotsky from the Houghton Library of Harvard University. The result of the study was an outline of the activities of Trotsky – Zinoviev supporters in the underground. We have identified key places of agitation, channels of communication with exiled oppositionists. It was possible to demonstrate that the transition to underground struggle was the result of difficult and lengthy discussions of op-position groups University students and teachers often played a key role in organizing the underground. Alt-hough the activities of the opponents of the Central Committee had local successes, they were soon defeated. The reason for this was not only the intensification of repression, but also the extreme disunity of the Leningrad oppositionists themselves.