Helicobacter pylori infection (Hp-I) has been associated with a wide spectrum of gastrointestinal and extra-digestive manifestations, including neurodegenerative diseases. Contradictory data have been published on Hp-I and multiple sclerosis (MS) association, with studies mainly using serology for Hp-I detection that cannot distinguish between active and past infections. We herein hypothesize that humoral and cellular immune responses induced by active Hp-I, beyond damaging locally the gastric mucosa, they may shape the character of systemic autoimmune responses, contributing to MS pathogenesis. To investigate our hypothesis, active Hp-I has been diagnosed in two small MS Greek cohorts by using primarily gastric mucosa histology. A higher prevalence of active Hp-I was documented in MS patients vs. controls (86.4 vs. 50%, P = 0.002)accompanied by exclusive existence of duodenal ulcer and autoimmune diseases with endoscopic and histological findings of chronic active gastritis for the MS group. Our preliminary data suggested that active Hp-Iunlike other studies, may not protect, but contribute to MS and we proposed possibleHp-relating mechanisms involved in MS pathophysiology, that merit further evaluation.