Alongside gastroduodenal diseases, Helicobacter pylori (H. pylori) infection has been associated with extradigestive diseases, including dementia. To identify all publications on the association between H. pylori and dementia, a MEDLINE search of all studies published in English from 1965 to 2007 was carried on. Very few investigations were found. Furthermore, studies with sufficient powerful design did not exist; dementia as well as H. pylori infection were defined with a low degree of homogeneity, biases were obvious in the control groups, thus giving room for large variation in the adjustment of potential confounding factors. Future research should be focused on three main issues: 1) prospective population-based studies, aiming to evaluate the consistency of epidemiological data with etiological hypotheses, and to provide the basis to develop and evaluate preventive procedures and public health practice; 2) intervention trials; 3) studies of physiopathology (both in the animal model and humans) to understand the potential biological plausibility of the association between H.pylori and dementia.