PURPOSE: The antimicrobial resistance of Helicobacter pylori is one of the critical factors in failure of eradication therapy. The purpose of this study was to evaluate antimicrobial resistance of H. pylori in Korean children. METHODS: Gastric mucosal specimens for H. pylori were obtained from children with dyspepsia who were cared for at Asan Medical Center Children's Hospital in Seoul, Korea between 2003 and 2009. Antimicrobial resistance tests were performed using the disk diffusion method for clarithromycin and amoxicillin and the E-test for metronidazole and tetracycline. Most children with H. pylori infections were treated using triple therapies. RESULTS: Thirty-three children had positive H. pylori cultures, although a resistance test was only performed in 28 patients. Resistant strains were found in 9 children (32.1%). The resistance rates to clarithromycin and metronidazole were 25% and 17.8%, respectively. There was no resistance to amoxicillin or tetracycline. The resistance rates decreased from 44.4% (2003~2006) to 26.3% (2006~2009) during the study period. CONCLUSION: Korean children demonstrated relatively high antimicrobial resistance to H. pylori in this study. However, there was a temporarily decreasing trend during the study period. A larger multi-regional study may be needed to determine the optimal antimicrobial treatment for pediatric patients infected with H. pylori.