Depending on the character for the Helicobacter pylori (HP) to decompose the urea by its endogenous urease, we have investigated the possibility to diagnose HP infection by 13C-urea breath test in 55 cases. Also, we compared the diagnostic results from 13C-urea breath test with those from culture, histology, and rapid urease test. The satisfied accuracy for the detection of HP infection with 13C-urea breath test was indicated.