In Japan, the noninvasive diagnostic tests currently approved for health insurance by the Ministry of Health are the serology test, the 13C-UBT test and the stool antigen test. The serology(antibody detection) test is useful for pretreatment screening, but because it reflects an immunologic response, false negatives are seen in patients with diseases such as rheumatoid arthritis and connective tissue diseases, and in the elderly. Furthermore, the serology test is difficult to use in the clinical setting, because 6 months or more is needed for the antibody titer to fall, after eradication therapy. For UBT, the expensive 13C-UBT is used. In view of the anticipated increase in testing, a test that is relatively inexpensive, simple, accurate and safe is needed. The stool antigen test has become available, and the test has been validated for accuracy. The stool antigen test is useful for the diagnosis of H. pylori infection before and after treatment in Japanese population.