Background: Vomiting is a very common and bothersome expression of seasickness. Previous works have shown that Helicobacter pylori infection may be related to vomiting resulting from nongastrointestinal causes, and physiological research has revealed that H. pylori may alter gastric motility. These findings, along with anecdotal case histories, led us to suspect that H. pylori infection may be related to the vomiting of seasickness. The objective of this study was to evaluate the association between H. pylori infection and seasickness susceptibility. Methods: Participants were 90 healthy, male, naval crew members 19.5 to 25 years of age. Forty-five were susceptible to seasickness, and 45 were nonsusceptible control subjects. Quantitative analysis of IgG levels for H. pylori was performed with an enzyme-linked immunosorbent assay. Results: The rate of H. pylori infection was 38% in the susceptible group, compared with 31% in the nonsusceptible group (p = 0.5). The titer of antibodies to H. pylori among case subjects was 81.2 U/mL (95% confidence interval, 11.5-151.1 U/mL), compared with 31.1 U/mL (95% confidence interval, 0.1-65.1 U/mL) for control subjects (p = 0.2). Conclusion: The current study does not support an association between H. pylori infection and seasickness susceptibility among sailors.