Background:It is well known that chronic gastritis induced byHelicobacter pylorimay be associated with hypochlorhydria and may also be accompanied by low levels of vitamin C in plasma and gastric juice in adults. This study investigates the relationship betweenH. pyloriinfection and vitamin C levels in the blood, plasma and gastric juice and the gastric juice pH of Korean children.Methods:During a 5‐year period, multiple gastric antral biopsies were taken from 452 children who underwent gastroduo‐denoscopy. The biopsy specimen was inoculated into phenol red buffered urea broth and incubated for 48 hours to detect color changes. The histopathologic findings were evaluated using the Sydney System. Concentrations of vitamin C in whole blood, plasma, and gastric juice aspirate were measured using the 2,4‐dinitrophenylhydrazine method.Results:Four hundred fifty‐two patients (228 boys, 224 girls) aged 1 to 15 years were enrolled in this study.H. pyloriwas detected in 112 patients (24.8%) using histology, whereas it was found in 204 patients (45.1%) using the urease test. One hundred seven patients (23.7%) had active gastritis, and 421 patients (93.1%) had chronic gastritis. Vitamin C levels in whole blood, plasma, and gastric juice exhibited significant negative correlation with the age of patients, the histologic density ofH. pylori, the degree of active and chronic gastritis, and the severity ofH. pyloriinfection (based on urease positivity and histologic density ofH. pylori). Gastric juice pH was correlated with the degree of chronic gastritis and was significantly higher in urease‐positive patients.Conclusions:The data demonstrate that vitamin C levels in whole blood, plasma, and gastric juice and the gastric juice pH in Korean children are closely related to the severity ofH. pyloriinfection and the histologic changes in the stomach. These data suggest that vitamin C may play a role in determining infection and progression, and vitamin C supplementation may be an important axis for the management ofH. pyloriinfection in children.JPGN 37:53‐62, 2003.