The purpose of this study was to evaluate whether the optimum prepara-tions are used for the second-line eradication therapy for Helicobacter pylori (H. pylori) infection in Japan. In the therapy, commercial tablets, which have 250 mg of amoxicil-lin (AMX) and 250 mg of metronidazole (MTZ), are used as antibiotics. The evaluation was performed by dissolution tests and simulations for intragastric drug concentrations based on the dissolution data. The dissolution tests were performed using the paddle method of Japanese pharmacopoeia XV. The data obtained were used for the simula-tion of intragastric drug concentrations. In dissolution studies, the 100% dissolution time (T100%) of AMX from the tablet which was about 20 min was faster than that from AMX alone (about 6 h). T100% of MTZ from the tablet which was about 3 h was later than that from MTZ alone (about 30 min). In simulated intragastric concentrations, the time above minimum inhibitory concentration (MIC) of the AMX tablet was 6.6 h which was shorter than that of AMX (11.4 h). The Cmax of the MTZ tablet was 0.095 mg/ml which was lower than that of MTZ (0.190 mg/ml). However, AMX is a time-dependent antibiotic, longer duration above MIC is desirable. On the other hand, MTZ is a concentration-dependent antibiotic, higher Cmax is desirable. In conclusion, the commercial products are found to be not the best, and preparing an AMX pharmaceu-tical preparation with more sustained release characteristic and a MTZ preparation with more rapid release characteristic are considered to be very advantageous.