Helicobacter pylori is a relevant pathogen for gastroduodenal diseases in human beings. Although its eradication often improves gastroduodenal diseases, H pylori is acquiring an elevated rate of resistance to various antimicrobials, such as metronidazole, clarithromycin, tetracycline and amoxicillin. Multi-drug resistance is a major problem to select the appropriate treatment of infectious diseases. To improve our understanding on the com-plexity of the problem, in this article we review the resistance mechanisms and give an update on H pylori antimicrobial resistance (Rev Méd Chile 2003; 131: 1313-20)