Objective. Because Helicobacter pylori creates a well-sheltered microenvironment within the gastric mucus layer, it has been speculated that the disruption of this space by a mucolytic agent may enhance the eradication rate. The aim of the present study was to investigate the effect of erdosteine, a strong mucolytic agent, on the effectiveness of PPI-based, first-line triple therapy in the eradication of H. pylori. Material and methods. Initially, 196 patients were enrolled to the study. Of these, 79 H. pylori-positive patients were randomized to the erdosteine group (triple therapy consisting of pantoprazole, amoxicillin and clarithromycin plus erdosteine; n = 40) or the placebo group (triple therapy plus placebo; n = 39) for 14 days. Endoscopic biopsies and <SU13</SUC-urea breath tests were performed at entry and at 4-6 weeks after the completion of the treatment. Additionally, rapid urease tests were performed at entry. Results. The eradication of H. pylori was achieved in 30 (75%) of the 40 patients in the erdosteine group and in 20 (51.3%) of the 39 patients in the placebo group, according to the ITT analysis (p = 0.028). When the PP analysis was performed as well, H. pylori eradication was achieved in 30 (78.9%) of the 38 patients in the erdosteine group and in 20 (52.6%) of the 38 patients in the placebo group (p = 0.016). Conclusions. Erdosteine is an efficient adjuvant therapy that could be used in conjunction with first-line triple therapy in the treatment of H. pylori.