We attempted to evaluate the appropriate time point for the assessment of Helicobacter pylori eradication after treatment. One hundred and nine patients with gastroduodenal diseases were enrolled this study. All of them were received proton pomp inhibitor based triple therapy and diagnosed as eradication of H. pylori infection at initial assessment. They were followed up over six months. The diagnosis of H. pylori eradication was determined by rapid urease test, culture, histology and 13C-urea breath test (UBT), and the initial assessment of the eradication was performed on 31 ?? 90 days after finishing eradication therapy. Re-appearance rate of H. pylori after initial diagnosis of eradication was 4.6% (5/109), and the mean follow-up period of them was 16.3 months. The time period of initial assessment of eradication in these 5 patients were 35, 37, 42, 49 and 60 days after treatment, respectively. On the other hand, there were 6 patients who were diagnosed as failed of eradication therapy by 13C-UBT, and being success at following period. All of the 13C-UBT levels of these 6 patients were less than 10 ?? and were decreased within negative range subsequently. The time periods of initial diagnosis of these patients except one were within 2 months after treatment. It was concluded that the assessment time of H. pylori eradication should be performed over 2 months after eradication therapy.