Infection with Helicobacter pylori(H. pylori) is thought to be an important factor in the pathogenesis of gastritis, peptic ulcer and gastric cancer, and the 13C-urea breath test (13C-UBT) is a convenient and non-invasive method for the detection of H. pylori in the stomach. We have examined the sensitivity, specificity and accuracy of 13C-UBT, comparing it with histology. The 13CO2/12CO2 ratio was measured by using infra-red spectroscopy(IR) and gas chromatography/mass spectrometry(GC-MS). The IR analyzer should be particularly useful for the diagnostic test of H. pylori infection using 13C-UBT.