BACKGROUND/AIMS: The aim of this study was to evaluate the changes in prevalence and the related factors of Helicobacter pylori (H. pylori) infection in Korean health check-up subjects during the period of 8 years. METHODS: Among 89,231 subjects who visited the Health Promotion Centers of Severance hospital or Chung-Ang University hospital from Jan. 1998 through Dec. 2005, a total of 10,553 subjects who received esophagogastroduodenoscopy (EGD) and H. pylori test were enrolled. H. pylori infection was assessed by histologic examination. Changes of the prevalence of H. pylori infection during 8 years, and infection-related factors such as demographic characteristics, body mass index, ABO blood types, endoscopic findings (presence of peptic ulcer diseases), educational level, economic status, smoking habits, and alcohol intake in year 2005 were analyzed. RESULTS: The mean age of 10,553 subjects (7,329 men, 3,224 women) was 49.7+/-10.4 years (range from 17 to 92 years). The prevalence of H. pylori infection at the first, second, third, fourth, fifth, sixth, seventh, and eighth year were 64.7%, 58.1%, 54.2%, 50.4%, 48.9%, 49.5%, 39.6%, and 40.0%, respectively, and these serial decreases in prevalence over 8 years were statistically significant (p<0.001). Regardless of sex, age or EGD findings, the prevalence of H. pylori infection was significantly decreased. In the analysis of the H. pylori infection-related factors in 2005, only age and EGD findings (peptic ulcer diseases) were significant factors. CONCLUSIONS: The prevalence of H. pylori infection was significantly decreased during 8-year period in Korean health check-up subjects. Age and peptic ulcer diseases were the two significant factors related to H. pylori infection in Korea.