We investigated the effect of H. pylori therapy on serum concentrations of pepsinogens on 87 patients of gastro-duodenal disease. In addition, we intended to see whether serum pepsinogen can serve as markers of response to H. pylori eradication. In 48 successfully eradicated cases, there was a significant decrease in gastritis score, and was a significant fall in serum pepsinogen II (PG II) level, and was a significant increase in pepsinogen I/II ratio (PG I/II ratio). In contrast, no change in gastritis score, PG II, and PG I/II ratio were observed in 39 unsuccessfully eradicated patients. No change in serum pepsinogen I (PG I) level was observed in both groups. In provisional successfully eradicated cases in PG II of decrease greater than 30% in after treatment, there was a sensitivity of 83.3% and a specificity of 89.7%. For the PG I/II ratio of increased greater than 30% in after treatment, the sensitivity was 95.8%, and the specificity was 94.9%. These findings suggest that PG II, PG I/II ratio can be useful for clinical evaluation of eradication therapy.