Meningitis is a common life threatening disease which may be caused by a bacterium, fungus, or virus. Here, the presence of a Helicobacter pylori antigen was investigated in serum and CSF samples from 173 individuals with meningitis. The influence of H. pylori infection on CSF levels of Thl/Th2 cytokines was also evaluated. H. pylori antigen was detected using ELISA and Western blot based on specific anti-H. pylori antibody. Thl/Th2 cytokines (IFN-gamma & IL-10, respectively) were also determined. A target epitope of 58-kDa was detected in selected CSF and serum samples using Western blot. H. pylori antigen was detected in the CSF samples of 75% of meningitis patients showing H. pylori antigen in their sera. A significant correlation (p < 0.001, r = 0.21) was shown between serum and CSF levels of 58-kDa H. pylori antigen. Only the levels of Thl cytokine (IFN-gamma) were significantly higher (p < 0.05) in CSF of meningitis patients positive for H. pylori antigen than negative patients with meningitis. In conclusion, the 58-kDa H. pylori antigen crossed the blood brain barrier and entered the CSF of patients with meningitis. A significant upregulation of Thl response may be associated with H. pylori infection in patients with meningitis.