BACKGROUND The seroprevalence of immunoglobulin G antibodies against Helicobacter pylori in endoscopy personnel was determined to investigate whether gastrointestinal endoscopists and endoscopy nurses in Japan are at an increased risk for H. pylori infection and to clarify risk factors for H. pylori infection during endoscopy. METHODS One hundred twenty-one gastrointestinal endoscopists and endoscopy nurses provided personal information, including their observance of infection-control measures, by means of self-administered questionnaire. One hundred one age-matched healthy individuals undergoing routine physical examinations served as controls. Serum samples from each subject were examined with enzyme-linked immunosorbent assay for the presence of IgG antibodies against H. pylori. RESULTS Among younger subjects (< 40 years old), endoscopists and endoscopy nurses had higher seropositive rates than did control subjects (p < 0.05). Among older subjects (> or = 40 years old), the seropositive rate did not differ between endoscopy personnel and control subjects (p = 0.2174). However, among older seropositive subjects, endoscopy personnel had significantly higher antibody titers than did control subjects (p < 0.01). Older seropositive endoscopists performed significantly more examinations per month than did their seronegative colleagues (p < 0.05). Furthermore, younger seropositive endoscopy nurses performed significantly more examinations per month than did seronegative nurses (p < 0.05). CONCLUSIONS Gastrointestinal endoscopists and endoscopy nurses in Japan are at high risk for H. pylori infection. The risk of H. pylori infection is correlated with the frequency of endoscopic examinations, especially in older gastrointestinal endoscopists and younger endoscopy nurses.