We investigated the utility of a 10-min 13C-urea breath test (13C-UBT) using 100mg of 13C-urea; this is a simple and rapid method for the detection of Helicobacter pylori infection. One hundred and fifty-one patients in whom the identification of H. pylori was established by rapid urease test, culture, and histology of six biopsy specimens underwent 254 13C-UBT examinations before and/or after eradication treatment. In the 133 patients who did not receive eradication treatment, the calculated sensitivity of the 10-min 13C-UBT was 99.4% and specificity 100% when the cut-off point was set at 3.5/1000, using a mass spectrometer. In the 121 patients who received eradication treatment, this cut-off point gave a sensitivity of 86.7%, a specificity of 99.1%, and a positive predictive value of 92.9%, with a negative predictive value of 98.1%. There were no significant differences between the diagnosis of H. pylori infection at 1 month and more than 3 months after the endpoint of eradication treatment. The 10-min 13C-UBT is suitable for the diagnosis of H. pylori infection before and after eradication treatment.