A prospective survey to investigate the seroprevalence of IgG against Helicobacter pylori among endoscopists in Taiwan was conducted by analyzing blood samples of 70 study subjects and 64 nonendoscopist physicians with quantitative ELISA. Personal information and the practices of infection control related to gastroscopy examination were obtained by a self-administered questionnaire. Significant differences were detected in the IgG prevalence between study and control subjects (80.0% vs 51.6%; P < 0.05). The serum level of antibody in endoscopists (385.2 +/- 36.1 unit/ml) was significantly higher than that of nonedoscopists (211.8 +/- 33.0 unit/ml; P = 0.018). Endoscopists performing 30 or more sessions of gastroscopy per week had higher seroprevalence than those performing less than 30 sessions (90.9% vs 70.3%; P = 0.0126). In conclusion, endoscopists in Taiwan had a high prevalence of H. pylori infection. The cause might be related to the frequency of gastroscopies performed.