Now that treatment of H. pylori associated disease is becoming common in Japan, drug resistant--H. pylori has emerged as a problem to be solved. There is no standard method of H. pylori drug susceptibility test in Japan yet. There are several methods available: Disk test, E-test, microplate method and agar plate dilution method. The E-test is being the standard method in European countries and USA. However the microplate method has been reported as a same accuracy as the agar dilution method, and thought as being a new standard method in Japan. In 2000, The Japanese Society of Chemotherapy proposed that drug susceptibility test be standardized and listed the break point of MIC of amoxicillin(AMPC) and clarithromycin(CAM).