Background: Antimicrobial resistance is one of the main obstacles for an effective eradication of H. pylori infection. Aim: To determine the susceptibility of H. pylori strains obtained from gastric biopsies to metronidazole, clarithromycin and amoxicillin. Material and methods: Susceptibility to metronidazole, clarithromycin and amoxicillin was determined using E-test in 46 isolates ofH. pylori obtained from gastric biopsies of 54 adult patients. Results: Thirty three percent of isolates were resistant to metronidazole and 2% were resistant to clarithromycin and amoxicillin. One isolate was resistant to metronidazole and clarithromycin. Conclusions: The antimicrobial susceptibility of these strains ofH. pylori obtained from Paraguayan patients, may help to decide the initial therapy to eradicate this infection (RevMéd Chile 2007; 135:1009-14)