In order to evaluate the value of serology and 14C-urea breath test in monitoring the effect of anti-Helicobacter pylori chemotherapy, at the first stage of this study, endoscopy, 14C-urea breath test and serology (H. pylori IgG antibody measured by ELISA) were performed in 42 of patients before the onset of anti-H pylori chemotherapy and at 1, 3, 6 and 12 months after termination of the treatment. On analyzing the change of the results of breath test and serology during the one year follow-up period in these patients, "above the cutoff value" in breath test and "reduction of A value less than 15% when comparing with pretreatment" in serology were made as the H. pylori positive criteria for monitoring therapeutic effectiveness on H. pylori. At the second stage of this study, total of another 63 of patients were studied to test the accuracy of the monitoring criteria. The results showed that the sensitivity of breath test was all 100.0% and specificity 95.5% and 100.0% respectively at 6 and 12 month after termination of treatment, the sensitivity of serology was all 100.0% and specificity was 50.0% and 83.3% respectively. A scheme for monitoring the effect of anti-H. pylori chemotherapy by combination of 14C-urea breath test and serology is proposed based on this study.