Background: Serum pepsinogen II (sPGII) levels are known to increase during Helicobacter pylori infection. Aim: To assess H. pylori infection and success of H. pylori therapy by means of sPGII levels. Methods: sPGII levels were determined in 156 H. pylori-positive and 157 H. pylori-negative consecutive patients with dyspeptic symptoms. Additionally, sPGII determination was performed in 70 H. pylori-positive patients 2 months after H. pylori eradication therapy. In 29 of these 70 patients, gastroscopy was performed to evaluate the effect of H. pylori therapy on gastric activity. Results:H. pylori-positive subjects demonstrated a significantly higher mean of sPGII levels than H. pylori-negative subjects (16.8 ± 7.4 vs. 8.6 ± 3.7 μg/l; p < 0.001). The best sPGII cut-off for predicting H. pylori infection was 9.93 μg/l (sensitivity 83%, specificity 73%). The best cut-off values to evaluate success of therapy were: sPGII of 9.47 μg/l, a sPGII variation level (difference between baseline and after therapy) of 4.54 μg/l, and a sPGII Δvalue (sPGII variation divided by sPGII before therapy) of 25% (sensitivity 93%, specificity 91%). Conclusions: sPGII levels may be used as a reliable marker of H. pylori infection in the initial diagnosis as well as to evaluate H. pylori eradication and subsequent changes in gastric inflammation. Copyright © 2004 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]